Xaanhal instance changes

Due to Xaanhal giving out far too much experience than intended, I've made a couple of tweaks.

* The instance will now reset every 2 hours, starting from time of entry.
* The mobs in the instance will give a little bit less experience than the mobs outside it.
* The instanced mobs will not count for Great Hunt points.

Penned by my hand on an unknown date.