Add functionality to Gerritlib to set project descriptions

Enabled functionality into gerritlib for setting descriptions
when creating a project, or have the ability to update
existing projects to update their descriptions.

This will allow jeepyb to create projects into Gerrit
having proper descriptions.

Change-Id: Id7fdef1599e8632edbdd8af5255207c18c9da7e0
Closes-Bug: #1349372
Merge "Add functionality to Gerritlib to set project descriptions"