Add basic block events

Add license headers
Fix LiquidSpreadEvent
And re-add renamed file...
Merge branch 'master' of https://github.com/SpongePowered/SpongeAPI into blockevents
Merge remote-tracking branch 'origin/blockevents' into blockevents
Add block break causes

Add license headers
Merge branch 'blockevents', remote-tracking branch 'upstream/master' into blockevents
Add more block causes, move things, fix Javadoc...

Add license headers
Merge branch 'blockevents', remote-tracking branch 'upstream/master' into blockevents
Rewrite block cause system to be more extensible
Merge branch 'blockevents', remote-tracking branch 'upstream/master' into blockevents
Make Cause a class, add new Reason, move things
Extend CauseTracked
Merge branch 'blockevents', remote-tracking branch 'upstream/master' into blockevents
Merge branch 'blockevents', remote-tracking branch 'upstream/master' into blockevents
Add BlockBurnEvent, BlockIgniteEvent, BlockChangeEvent

Add license headers
Merge branch 'blockevents', remote-tracking branch 'upstream/master' into blockevents
Add SignChangeEvent and fix some bugs
Add bulk block events and change event class inheritance.

* Adds BulkBlockEvent to handle bulk block events.
* Makes some proposed events extend BulkBlockEvent.
* Makes place/break events player-specific and makes them extend BlockChangeEvent.
* Adds BlockInteractEvent for when a block is interacted with.
* Changes PlayerChangeSignEvent to extend BlockInteractEvent.
Add a few more block events.