* New command-line tool: doodle-admin for signing license keys for
users. Includes functions to initialize a keypair, sign license keys
and validate existing keys.
* The Main Menu screen shows a blue "Register Game" button in the bottom
right corner of the screen, for unregistered users only.
* In Edit Mode, there is a "Help -> Register" menu item that opens the
License Window.
* The License UI Window lets the user select the license.key file to
register the game with. If registered, a copy of the key is placed in
Doodle's profile directory and the licensee name/email is shown in the
License UI window.
* Unregistered games will show the word "(shareware)" next to the title
screen version number and Edit Mode status bar.
* No restrictions are yet placed on free versions of the game.
