Item and weapon added events. Upgrade to MonoGame 3.0.1.0

Updated engine to implement MonoGame 3.0.1.0. This allows us to upgrade
the solution to be developed in Xamarin Studio instead of MonoDevelop
3.x.  Added events, args, and delegates for weapon and item add. "Give"
methods will scavenge what ammo/units they can if the weapon/item
already exists in inventory.