[WIP] Redstone framework

This is just the start of the framework as I gradually transplant my prototype (https://github.com/iamgreaser/rsproto) to the actual Glowstone framework. (At this stage you should look at RSWorld.java to see how the prototype implements it, because it'll end up looking very similar.)

This is for issue #116 Redstone Support. I will probably drop the WIP tag once the subset I'm focused on is stable enough, and do a separate pull request for the finer aspects of Redstone.

Current status:
* **DONE** - RSManager class tied to world to handle the redstone network
* **DONE** - Chunks are dirtied, updated and unloaded by GlowWorld and GlowChunk
* **DONE** - pulse() method hooked up to GlowWorld
* **DONE** - Actually load chunk data into RSManager
* **DONE** - Redstone torch blocks
* **WIP** - Basic redstone logic
  * **DONE** - Redstone torch->solid->torch sequence
  * **WIP** - Redstone wires
* **FIXED ITSELF?!** - Actually relay redstone updates to client (should be there BUT there's some stupid bug somewhere which is preventing this from actually working)
* **DONE** - Prevent placement of redstone dust ("wires") on a lot of things (mostly RS dust, RS torches)

To be implemented in later pull requests:
* Block diagonal-down/up when blocked by, well, a block
* Actually deregister chunks properly
* Faster deregistering of chunks
* Redstone wire "injection" into solids
* Proper network creation which doesn't require tracing wires every pulse (prototype uses HashSets to mark positions of "sources", torches, and charged wires - it's not going to hit *every* block each frame!)
* Repeaters
* Proper analogue values for wires
* Comparators

Stuff like this should go at the top of your class.