Add EventBus Library

Start converting intents and broadcast receivers to use EventBus library
Credit EventBus library in preferences
Check which change list is refreshing before showing animation
Remove unused DefaultGerritReceivers
Get correct date when searching for older changes
Fix SearchKeyword.retainOldest to actually use the oldest search keyword
 not the newest. This should fix not loading older changes.

Change-Id: I6b4b1a4b3ba172d24dc2f03d90100d5889be10c8