Add selection feature to NavigationDrawerView.

The selected item can be marked by MenuItem#setChecked in
onNavigationItemSelected callback. This also takes MenuGroup into
account, that is, NavigationDrawerView highlights only one item in one
MenuGroup.

Also removes an unnecessary separator when a MenuGroup comes at the top
of the menu.

Change-Id: Ia7373bb8b64836de8a0db7552c5304165afa7d64
8 files changed