Add docs for event log usage
Add docs for event log usage

Add development documentation and useful notes for devs.

Change-Id: I380a9495e1b85bd73499b535323c87ce84e0ef62

egafford/sahara,openstack/sahara,ekasitk/sahara,matips/iosr-2015,redhat-openstack/sahara,ekasitk/sahara,matips/iosr-2015,zhangjunli177/sahara,openstack/sahara,tellesnobrega/sahara,esikachev/sahara-backup,henaras/sahara,matips/iosr-2015,esikachev/sahara-backup,crobby/sahara,bigfootproject/sahara,esikachev/sahara-backup,zhangjunli177/sahara,redhat-openstack/sahara,zhangjunli177/sahara,ekasitk/sahara,egafford/sahara,crobby/sahara,bigfootproject/sahara,tellesnobrega/sahara,redhat-openstack/sahara,zhujzhuo/Sahara,bigfootproject/sahara,henaras/sahara,henaras/sahara,zhujzhuo/Sahara,zhujzhuo/Sahara,crobby/sahara