Rename plugin

First proposal for the rename plugin #108. It only supports cut for now and I finally settled with C because I think cleaning up the C++ interface should be handled in a different step. Please let me know if it works especially with OpenICC.
just use "name" or "origname" and also document that in doc/METADATA.ini

"rename" won't be the only implementation, so its not a good idea to encode the pluginname there.