Minor style fixes.
Fixed support for 1.8's string-based item ids.
Convert data types during server.properties migration (fixes #392).
Added player visibility API (closes #121).

Players are hidden fron another player's tab list and entity updates.
Also renamed other canSee methods to canSeeChunk and canSeeEntity.
Add bonemeal interaction with saplings
Work something much more generic
Extend BlockPumpkinStem, BlockMelonStem and BlockTallGrass from BlockGrowable
Change to IBlockGrowable, add BlockGrass
Add BlockDoublePlant, modify BlockTallGrass
Add BlockPlant, BlockCrops and BlockDeadBush
Add ItemHoe
Add ItemSeeds, BlockStem, modify BlockCrops and remove BlockPumpkinStem, BlockMelonStem
Add ItemFoodSeeds, ItemFood and BlockCarrot, BlockPotato
Add ripe() method to BlockStem
Add BlockMushroom and huge mushrooms generation
spawn some green villager particles (needs isFertilizable() filtering)
Add BlockCocoa and BlockPumkin, add cocoa beans interaction
Add isFertilizable() and canGrowWithChance() methods to IBlockGrowable, and implementations
Change BlockStem ripe method to apply east, west, north then south priority like vanilla
Prepare things for BlockGrowEvent