Initial work on a portable computer (carried in player inventory) to test the API.
Merge branch 'master' of github.com:MightyPirates/OpenComputers into tablet

Conflicts:
	src/main/scala/li/cil/oc/Items.scala
	src/main/scala/li/cil/oc/client/GuiHandler.scala
Some fixes and a texture for the tablet prototype.
Merge branch 'tablet'
Added T2 redstone card. Closes #340.
T1 is now vanilla functionality (simple, analog redstone signals), T2 is for mod interop (bundled redstone, wireless redstone). Existing redstone cards are automatically converted to T2 cards, to avoid breaking things more than necessary. Redstone blocks behave like T2 cards, but without the wireless support.