Added a call to geogit's diff when a cell is clicked in the GeoGitHistory panel.
Fixed removal of the diff layer, somehow didn't commit it last time.
Added a check to ensure it is a GeoGit layer being removed before hiding the history panel.
Right clicking on a layer will now give the user an option to show or hide the GeoGit history panel.
Merge commit 'bdd504f3a2b7f924ed8553bdcb5f0cb6c6e69417'
Merge commit '17a831b0e5fab2b04f63f97cb34e41dd788e4b93'

Conflicts:
	webapp/src/gxp/script/plugins/GeoGitHistory.js
Fixed a bug with adding features.

It was trying to build a log call with the feature id of a feature that wasn't fully created yet. Added a null check for the feature id.