Added complete Doc Conventions in common guide.

backport: havana
Change-Id: I6851ef705247d619e78fb63cbcdf1ce804a548f1
Partial-Bug: #1121866
Merge "Added complete Doc Conventions in common guide."
Fixed Typo

Changed with to Wish

Change-Id: I33895c70cb736c4ade8aecb4e125419727556474
Merge "Fixed Typo"