Changed the signature of setUp() method at NavigationDrawerFragment
Removed commented old code
Uncommented two lines of setup ActionBar
Minor changes in xml files
Code refactoring

- changed the name and rules of using the navigation drawer 'on item
  click' listener
- separated method to changing fragments
- added some comments
Refactoring of NavigationDrawerFragment
Removed DrawerToggle

DrawerToggle is redundant for now.
Renamed and relocated classes related to navigation drawer
Renamed private fields (MainActivityHelper)
Renamed interfaces

 - InterfaceFragment to IFragment
 - InterfaceMainActivity to IMainActivity
Added a comment to NavigationDrawer