[feature] Add XMPP presence and description support for current game status with Essentials XMPP

The attached pull includes support for logging into an XMPP server and providing game status information, including how many players are online.  As more then 1 user connects to the server, the presence status will change red to indicate the server is busy with descriptive information and user online count.  This includes support for task scheduling of the presence update as players log on/log off the server to provide minimal impact or delay to gameplay.

![xmppfun2](https://f.cloud.github.com/assets/5677937/1322714/2972fe52-3445-11e3-90a8-05bbba08d780.PNG)