improve permissions api
improve permissions api

move permissions package to providers package

broke up IPermissionsProvider into multiple interfaces based on provider abilities

removed group permissions methods from vault and bukkit provider.

added VaultGroupProvider which is used if vaults underlying permission provider has group support.

use IPermissionGroup instead of String[] for returning permission group collection.

Permissions utility provides methods for getting the provider based on ability

JCThePants/PV-StarAPI,JCThePants/PV-StarAPI