Slight visual fix to web ui
Updated the Servlet to return Validation Exception if there is an issue wi th a request. Updated the UI to display the error message
Refactored the servlet's DeviceNotifier
Updated SyncMessage to a GCMSyncMessage
Added a mock implementation of DeviceMapper
Updated Spring config to manually define the controllers + inject thier dependencies
Cleaned up the code, removed unnecesary comments
Added tests to test device manager