Added Menu, with Newsstand, Settings, and About options.
Newsstand option returns user to main activity (NewsstandActivity);
Settings opens the Settings activity (SettingsActivity), which currently
displays text;
About opens a dialog to display information about the app.

Also implemented ActionBar icon navigation.  Pressing the ActionBar icon
will return the user to the main activity (NewsstandActivity).
Added 'plus' button to nav_menu,
Created add_newsrack layout and AddNewsrackActivity
Added menu functions to Newsstand Activity