Port align-layers to GimpProcedureConfig
This ports the Align Visible Layers plug-in to GimpProcedureConfig
.
It adds the options (previously GUI-only) to the procedure itself, so they can be configured via scripts.
Also, the warning about only having 1 layer originally only showed in the console. This was changed to use g_set_error ()
like other plug-ins so that it shows up in GIMP itself. Finally, mnemonics were added to all properties.