Fix resizes and abandonclaim

Previously, it was possible to resize and abandon claims while they were being rented/leased. This updates comes with a solution, but requires a modified version of GriefPrevention, until eventually it gets merged into the actual GriefPrevention alltogether.

/!\ THIS UPDATE WON'T WORK WITHOUT THE PROVIDED GriefPrevention.jar FILE /!\

This is still an experimental solution for issue #2

Future versions will include options to allow or disallow the owner access / containers / build permissions. Currently, a rented claim cannot have it's trustlist changed, and the owner loses all his permissions while the transaction isn't finished.