Beginning of Logout Feature

Basic functionality implemented for logout. Added menu item and basic
activity that removes database and clears stored username and password.
Still needed is a confirmation dialog at the very least.
Make the Database Name Accessible

Changed the value of DATABASE_NAME from private to protected so we can
get read-only external access to it from other classes. This will avoid
having to hard-code the database name in the delete call for logging
out.
Logout Dialog

The AlertDialog for the Logout feature (issue #35) is now complete.
Set up Logout Action in Home

Move the logout process from the Logout activity to Home. Also,
implement the Logout confirmation AlertDialog.

This closes #35
Remove Unneeded Logout Activity