Initial implementation of the feature diff panel.  Select a commit in the history panel then right click the panel and press the "show diff" button to show the changes made in the selected commit.
Right clicking on a feature in the diff panel will now give the user an option to zoom to that feature's location.
Merge branch 'FeatureDiffPanel'

Conflicts:
	webapp/src/app/app.js
	webapp/src/app/salamati/locale/en.js
	webapp/src/app/salamati/locale/es.js
	webapp/src/gxp/script/plugins/GeoGitHistory.js