Remove old downloads

All relevant versions of Corruption can be found on BukkitDev, so
there's no point in keeping these old builds
Refactor PermissionsManager & update dependencies

Refactored PermissionsManager to be included in the Corruption packages.
Updated versions of the Permissions plugins used in the
PermissionsManager.
Updated versions of mcMMO, Magicspells and Heroes to build with.
Bump version number to 2.3.2 and more

- Bumped version number to 2.3.2 for the new release
- Changed the onEntityDamage listener priority to HIGHEST. Corruption
should have the last say in what happens to Bosses in terms of damage
taking/dealing.