Fix opening of GUIs (with client/server sync) and fix Knapsack gui.

This:
* Fixes GUI opening code (In my previous pull request I only opened it client side)
* Actually sends packets of other events and syncs client and server NBT data on connect. (well, it would if it weren't for MinecraftForge/FML#381 which doesn't fire PlayerLoggedOutEvent). A workaround is to go to the nether (to fire onPlayerChangedDimensionEevent).
* Fixes the background of the knapsack GUI so it is in the correct spot.

![Uploading armorGuiFix1.png . . .]()

![Uploading armorGuiFix2.png . . .]()