Known bugs:
-----------
* The cancel progress signal scrambles up the internal state
  during changes apply (needs a new version of pdb, either
  supporting trapping or uncancelable progress)
* There's a call to deprecated gimp_layer_set_preserve_trans()
  instead of gimp_layer_set_lock_alpha(), should version-check somehow
  (problems with packages here)
* The "New" button is not working properly when dealing with
  floating selections
* The seam map is not properly translated
* see TODO for missing features