Added ActionBarSherlock, Navigation Drawer, Integrated Index application, Implemented gmail login

Converted required activities to fragments for better integration of Navigation Drawer.
Moved old Home screen menu to Navigation Drawer. 
Index application is the new default screen after login. 
Gmail login uses oauth2 token obtained using google play services.
Additional external dependencies:
1. ActionBarSherlock
2. Google Play Services
We usually pass 'item' in this method -> http://git.io/uPnbUg
 so that action bar home/up action opens/closes the navigation drawer. However, when we use ABS, passing 'item' gives
     
    The method onOptionsItemSelected(android.view.MenuItem) in the type ActionBarDrawerToggle is not applicable for the arguments (com.actionbarsherlock.view.MenuItem)

The only workaround I found is to override getMenuItem the way its mentioned here: http://git.io/IOkzRQ