Contextual action bar diff options

Add preference for viewing change diffs so clicking on a changed file
 card can open the internal viewer or view the diff in the browser,
 works with changed files header too
Added contextual action bar for long presses on any of the changed files
 cards to either open in the internal viewer or in the browser.
Added new 'view in browser' icon
Change internal diff viewer icon to old view in browser icon
Bump min-API level to 14 (ICS) - A method to provide data to the
 contextual action bar was added in ICS and none of our users run
 versions less than ICS.
Selected card changes background when pressed/selected
Close the CAB when the selected item is hidden

Patch Set 4: Fix build

Change-Id: If9e939620c88bee5b01ac49cdcbd87bc5351ec05