Revamped place and dig event handling.

Throw BlockBreakEvents in creative (fixes #273).
Fix BlockPlaceEvents returning AIR (fixes #271).
Prevent block break with swords in creative (fixes #214).
Simplified dig and place logic slightly.
Added basic potion effect definitions (fixes #295).
Added checkstyle and fixed code to obey it (thanks @meggawatts).
Merge pull request #3 from GlowstoneMC/master

Merge