Continuation of @wow4201's Item Frames

This is a continuation of Item Frames support, started by @wow4201.

I've made some checkstyle fixes, and prevented item from being removed from a player inventory in Creative.

Glowkit: https://github.com/GlowstoneMC/Glowkit/pull/52

@wow4201: If you decide to pick this up again, I'll close this PR and give all the code to you.
Well, it drops an item, but you can't pick it up or interact with it property.