onPacket and getChat expect to receive a bare JID.

onPacket and getChat expect to receive a bare JID. This caused an exception at com.xabber.android.data.message.MessageManager.addChat(MessageManager.java:166) when xabber observed another presence send a message to a contact and that contact respond thereafter.

This reverts commit 70021300.

Invalid timestamp for persistent notification (Closes #123)

Export chat in the background thread

Improvements for German translation