[ADD] ContactsActivity got a ListView to show all contacts.
[ADD] ArcanumContactCollection to hold a list of contacts.
[ADD] Task to get unreaded messages.
[ADD] MessageService to manage push messages. This service will send a event to the current MessageActivity or will create a notification.
[ADD] HashCode-Calculation for ArcanumContact to make it easy comparable.
[CHG] URL to send and get messages from GAE.
[CHG] Migrate GAE Datestore from old DB to NDB.