[Android] [URNG-366] Add "Game over" functionality in application 

Short description: User can now see notifications in application. Every ~10 seconds (this time can be changed) user is able to see one of the following notifications:

    * gameLost
    * gameWon
    * gameChanged
    * taskNew
    * taskChanged

Long description and changes made:

    * lines 364+ in NotificationServer.java are just mock methods of this class to simulate that new notifications are available. Most of the job was done already.
    * lines 53-131 in NotificationServer.java and file NotificationServerTest.java adds WebServer functionality to NotificationServer
    * added method "equals()" in classes: Task, UrbanGameShortInfo, UrbanGame to reduce code repetition
    * added method isApplicationRunning() in UrbanGameApplication class. I needed it to terminate asyncTask (asyncNotificationQuery in NotificationServer class), beacause when app normally exits the AsyncTask is not terminated with it.