Fixes for two crashing bugs in Inventory Manager

I found and fixed two bugs in Inventory Manager that would crash Minecraft.

The first occurs when you're moving an item into a particular slot in an inventory, and that slot and all later slots are full.  This would cause infinite recursion and a crash.

I'm not exactly sure what causes the second, but the symptom is that ComputerCraft throws an exception about trying to operate on a disconnected computer/turtle.  From the backtrace, the bad call was in BaseManager's queueEvent; I rewrote it to avoid calling queueEvent if the computer has disconnected, and haven't gotten the crash again since.

I've never done the github fork/pull-request thing before; I hope I'm doing it right...