ZEPPELIN-2873 - Add documentation on secure cookie in Shiro
ZEPPELIN-2873 - Add documentation on secure cookie in Shiro

### What is this PR for?
Adding a section in Shiro Authentication about how to enable secure cookie via Shiro. Shiro do support configuring 'HttpOnly' flag in response cookie. A Zeppelin user, who is security conscious, should know how to enable this in Zeppelin's Shiro configuration.

### What type of PR is it?
Documentation

### What is the Jira issue?
ZEPPELIN-2873

### How should this be tested?
Doc changes. CI test should pass.

### Questions:
* Does the licenses files need update? No
* Is there breaking changes for older versions? No
* Does this needs documentation? No

Author: Vipin Rathor <v.rathor@gmail.com>

Closes #2545 from VipinRathor/ZEPPELIN-2873 and squashes the following commits:

c7b7995 [Vipin Rathor] Updated doc as per the review comments.
fec8d7e [Vipin Rathor] ZEPPELIN-2873 - Add documentation on Zeppelin Shiro's abliity to configure secure cookie

Leemoonsoo/zeppelin,r-kamath/incubator-zeppelin,lresende/incubator-zeppelin,fogbeam/zeppelin_mirror,hammertank/zeppelin,sctincman/zeppelin,karuppayya/zeppelin,yu74n/zeppelin,herval/zeppelin,herval/zeppelin,tzolov/incubator-zeppelin,cquptEthan/incubator-zeppelin,chilang/zeppelin,doanduyhai/incubator-zeppelin,Leemoonsoo/zeppelin,zjffdu/zeppelin,namanmishra91/zeppelin,doanduyhai/incubator-zeppelin,Leemoonsoo/incubator-zeppelin,datalayer/zeppelin-datalayer,pellmont/zeppelin,prabhjyotsingh/zeppelin,prabhjyotsingh/zeppelin,tzolov/incubator-zeppelin,sctincman/zeppelin,astroshim/zeppelin,sravan-s/zeppelin,apache/incubator-zeppelin,apache/zeppelin,wary/zeppelin,sctincman/zeppelin,sravan-s/zeppelin,prabhjyotsingh/incubator-zeppelin,namanmishra91/zeppelin,joroKr21/incubator-zeppelin,astroshim/zeppelin,zetaris/zeppelin,cquptEthan/incubator-zeppelin,sctincman/zeppelin,joroKr21/incubator-zeppelin,r-kamath/zeppelin,sergeymazin/zeppelin,pellmont/zeppelin,tzolov/incubator-zeppelin,Leemoonsoo/incubator-zeppelin,VipinRathor/zeppelin,doanduyhai/incubator-zeppelin,apache/zeppelin,lresende/incubator-zeppelin,herval/zeppelin,karuppayya/zeppelin,sergeymazin/zeppelin,cquptEthan/incubator-zeppelin,namanmishra91/zeppelin,r-kamath/zeppelin,VipinRathor/zeppelin,Leemoonsoo/zeppelin,herval/zeppelin,Leemoonsoo/incubator-zeppelin,jongyoul/zeppelin,namanmishra91/zeppelin,joroKr21/incubator-zeppelin,astroshim/incubator-zeppelin,joroKr21/incubator-zeppelin,tinkoff-dwh/zeppelin,prabhjyotsingh/zeppelin,mwkang/zeppelin,zjffdu/zeppelin,apache/incubator-zeppelin,wary/zeppelin,hammertank/zeppelin,mwkang/zeppelin,astroshim/incubator-zeppelin,sergeymazin/zeppelin,zjffdu/zeppelin,jongyoul/zeppelin,astroshim/zeppelin,wary/zeppelin,r-kamath/incubator-zeppelin,zetaris/zeppelin,datalayer/zeppelin,mwkang/zeppelin,chilang/zeppelin,zetaris/zeppelin,datalayer/zeppelin,jongyoul/incubator-zeppelin,anthonycorbacho/incubator-zeppelin,datalayer/zeppelin-datalayer,zetaris/zeppelin,VipinRathor/zeppelin,astroshim/zeppelin,joroKr21/incubator-zeppelin,sravan-s/zeppelin,VipinRathor/zeppelin,r-kamath/zeppelin,sravan-s/zeppelin,astroshim/incubator-zeppelin,sergeymazin/zeppelin,zjffdu/zeppelin,fogbeam/zeppelin_mirror,joroKr21/incubator-zeppelin,sctincman/zeppelin,Leemoonsoo/zeppelin,tzolov/incubator-zeppelin,chilang/zeppelin,tinkoff-dwh/zeppelin,jongyoul/zeppelin,Leemoonsoo/zeppelin,zetaris/zeppelin,Leemoonsoo/incubator-zeppelin,astroshim/zeppelin,datalayer/zeppelin,datalayer/zeppelin,r-kamath/zeppelin,Leemoonsoo/incubator-zeppelin,pellmont/zeppelin,doanduyhai/incubator-zeppelin,yu74n/zeppelin,jongyoul/incubator-zeppelin,sergeymazin/zeppelin,astroshim/zeppelin,datalayer/zeppelin-datalayer,sctincman/zeppelin,sergeymazin/zeppelin,hammertank/zeppelin,chilang/zeppelin,herval/zeppelin,Leemoonsoo/zeppelin,apache/incubator-zeppelin,prabhjyotsingh/incubator-zeppelin,lresende/incubator-zeppelin,apache/zeppelin,anthonycorbacho/incubator-zeppelin,joroKr21/incubator-zeppelin,astroshim/incubator-zeppelin,astroshim/incubator-zeppelin,Leemoonsoo/zeppelin,hammertank/zeppelin,hammertank/zeppelin,fogbeam/zeppelin_mirror,r-kamath/zeppelin,lresende/incubator-zeppelin,fogbeam/zeppelin_mirror,r-kamath/incubator-zeppelin,anthonycorbacho/incubator-zeppelin,VipinRathor/zeppelin,jongyoul/zeppelin,jongyoul/zeppelin,doanduyhai/incubator-zeppelin,cquptEthan/incubator-zeppelin,r-kamath/zeppelin,pellmont/zeppelin,vipul1409/zeppelin,VipinRathor/zeppelin,jongyoul/zeppelin,namanmishra91/zeppelin,yu74n/zeppelin,jongyoul/incubator-zeppelin,joroKr21/incubator-zeppelin,cquptEthan/incubator-zeppelin,wary/zeppelin,karuppayya/zeppelin,tinkoff-dwh/zeppelin,cquptEthan/incubator-zeppelin,apache/incubator-zeppelin,tzolov/incubator-zeppelin,mwkang/zeppelin,herval/zeppelin,doanduyhai/incubator-zeppelin,cquptEthan/incubator-zeppelin,sravan-s/zeppelin,sravan-s/zeppelin,jongyoul/zeppelin,Leemoonsoo/zeppelin,zetaris/zeppelin,apache/incubator-zeppelin,vipul1409/zeppelin,zjffdu/zeppelin,datalayer/zeppelin-datalayer,karuppayya/zeppelin,jongyoul/incubator-zeppelin,tinkoff-dwh/zeppelin,datalayer/zeppelin,karuppayya/zeppelin,lresende/incubator-zeppelin,apache/zeppelin,tinkoff-dwh/zeppelin,hammertank/zeppelin,astroshim/zeppelin,fogbeam/zeppelin_mirror,prabhjyotsingh/incubator-zeppelin,pellmont/zeppelin,vipul1409/zeppelin,prabhjyotsingh/zeppelin,wary/zeppelin,wary/zeppelin,anthonycorbacho/incubator-zeppelin,zjffdu/zeppelin,anthonycorbacho/incubator-zeppelin,herval/zeppelin,fogbeam/zeppelin_mirror,jongyoul/incubator-zeppelin,chilang/zeppelin,sctincman/zeppelin,sravan-s/zeppelin,chilang/zeppelin,hammertank/zeppelin,vipul1409/zeppelin,zetaris/zeppelin,anthonycorbacho/incubator-zeppelin,doanduyhai/incubator-zeppelin,namanmishra91/zeppelin,vipul1409/zeppelin,apache/zeppelin,tzolov/incubator-zeppelin,datalayer/zeppelin,apache/zeppelin,datalayer/zeppelin,mwkang/zeppelin,VipinRathor/zeppelin,yu74n/zeppelin,yu74n/zeppelin,fogbeam/zeppelin_mirror,yu74n/zeppelin,r-kamath/incubator-zeppelin,apache/incubator-zeppelin,r-kamath/incubator-zeppeli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