Fixed computers failing to save when saved while performing a synchronized call on userdata.
Added a debug card item, allows manipulating the world some to make it easier to test stuff.
Still can't remember why top-level coroutine.yield() in programs wouldn't pull events... nothing seems to break, so there. Closes #483.
Also made sh add traceback to message when program crashes.
Merge branch 'master' of github.com:MightyPirates/OpenComputers into master-MC1.7.10

Conflicts:
	src/main/scala/li/cil/oc/server/component/machine/NativeLuaArchitecture.scala