Add a paragraph discouraging modification of upstream files
Add a paragraph discouraging modification of upstream files

We have an unwritten rule in Sahara about not modifying upstream
files, even for formatting. So, now it is a written rule in the
developer guide.

Closes-Bug: #1277584
Partial-Implements: blueprint update-docs-icehouse
Change-Id: Ic018f6fce7d30a90f5a144cf8efd75cb488ab45b

xme1226/sahara,zhangjunli177/sahara,esikachev/sahara-backup,zhujzhuo/Sahara,egafford/sahara,mapr/sahara,matips/iosr-2015,redhat-openstack/sahara,henaras/sahara,esikachev/sahara-backup,ekasitk/sahara,esikachev/sahara-backup,citrix-openstack-build/sahara,keedio/sahara,tellesnobrega/storm_plugin,bigfootproject/sahara,henaras/sahara,tellesnobrega/storm_plugin,ekasitk/sahara,esikachev/scenario,crobby/sahara,crobby/sahara,tellesnobrega/sahara,zhangjunli177/sahara,mapr/sahara,matips/iosr-2015,henaras/sahara,zhujzhuo/Sahara,keedio/sahara,tellesnobrega/storm_plugin,keedio/sahara,zhujzhuo/Sahara,mapr/sahara,matips/iosr-2015,openstack/sahara,bigfootproject/sahara,redhat-openstack/sahara,tellesnobrega/sahara,citrix-openstack-build/sahara,openstack/sahara,citrix-openstack-build/sahara,esikachev/scenario,ekasitk/sahara,zhangjunli177/sahara,bigfootproject/sahara,crobby/sahara,egafford/sahara,xme1226/sahara,xme1226/sahara,redhat-openstack/sahara,esikachev/scenario