Rewrote GFL-UserManagement

GFL-UserManagement now properly utilizes the SourceMod tools for authorization. This means that admins_simple.ini and other files are respected in such a way that all the flags are merged.

However, this means that users must reconnect in order to receive updated perks from the forums. sm_reloadadmin still works but it does not refresh from the API; it just reapplies cached perks.