Add /reportrts *version command with permission.

Added a sub-command for /reportrts to manually check if an update is available.

I'm not sure this will work, but here goes nothing.

* Added permission to RTSPermissions.java.
* Added permission to RTSListener.java so that it checks for permission instead of 'isOp'.
* Added permission to the plugin.yml with default of OP (so it replaces the isOp check).
* Added UPDATE command to ReportRTSCommand.java (checks 'versionChecker.upToDate')