ogre-tools: Allow to use more than one plugin.

Change-Id: I51f7a74451471514882238c7ee2ec593cbf0711d
Reviewed-on: http://gerrit.aldebaran.lan:8080/9712
Tested-by: jfremy <jfremy@aldebaran-robotics.com>
Reviewed-by: dmerejkowsky <dmerejkowsky@aldebaran-robotics.com>