Add TAB_NONE to extra EXTRA_TAB values

Allow an intent for starting NetworkActivity to explicitly specify that
it should not change tab using the TAB_NONE value for the EXTRA_TAB
extra.
Change target SDK version to 19 (KitKat 4.4)

Target version 19 of the Android platform SDK, corresponding to Android
4.4 KitKat. There's no good reason not to target the highest version I
can test on.
Add application settings activity

Add an activity for allowing the user to adjust application settings.
Currently there are no settings. The up button in the settings activity
takes the user back to the network activity.
Add nav and notification drawers to settings
Animate nav drawer close before fulfilling intent

When an item in the navigation drawer is selected by the user, animate
the closing of the drawer and only launch the appropriate activity when
it is closed.
Move navigation drawer code to DrawerActivity

DrawerActivity should be extended by any activity that wishes to have
the navigation and notification drawers. For activities not at the top
level, call `setDrawerIndicatorEnabled(false)` to show the standard up
button in the action bar.

DrawerActivity will inflate a wrapper layout that adds the appropriate
drawer views. Calling `setContentView` from a subclass activity will
actually fill the content subview, so it can be used as usual.

When the an item in the navigation drawer is selected, the drawer will
close and only once it has fully closed will the appropriate intent be
fired. During this time, touch interaction is disabled, to prevent the
user from interrupting the drawer closing animation.