Started on revamp of block and item type system.
Handle right-clicks on an ItemType basis. Added sign and sugarcane placement.
Added TileEntity system and implemented sign placement/editing/saving.
Updated mob spawner and note block to new system.
Added simple tests for ItemTable and made a couple minor tweaks.
Wholly revamped BlockPlacementHandler, and some other minor cleanup.
Made note blocks interactable, changed sign placement math, added a few item-blocks.
Quieted some logging, made gamemode change update allowFlight, and added several toString methods.