Update CraftBukkit to Minecraft 1.5.1
Implement unit test for hasGravity(). Adds BUKKIT-3832
Add Fish (Hook) entity to PlayerFishEvent. Adds BUKKIT-1025
Ignore all .DS_Store files, not just the one in the project root.
Add method to get the source of a TNTPrimed. Adds BUKKIT-3815
Add ability to modify ThrownPotion properties. Adds BUKKIT-3197
Stationary lava is also a LAVA ignition cause.
Add BlockDropper for diff visibility
Implement Dropper interface. Adds BUKKIT-3750
Cleanup and rework physical interaction events. Fixes BUKKIT-3686

Currently when dealing with physical interactions with pressure plates
and tripwires we immediately block their activation as soon as a single
entity involved has their event cancelled. We also fire events whenever
an entity intersects the block a wooden button is in even if they aren't
actually pressing it. To correct this we move the button interaction to
the correct place and modify all three to only block the activation if
every entity is blocked from using them instead of just one of them.
Merge branch 'master' of https://github.com/Bukkit/CraftBukkit