diff layer/LayerFactory.cpp @ 293:15b8a4bfe855

* continue to pick "new" colours for coloured layers even when all colours
  have been used at least once, rather than sticking on the last one
* some messing about with application palette settings
* when replacing an audio file, retain the previous playback settings for
  any layers that depended on the old file
* re-check plugin program setting when a parameter changes -- so a plugin
  can decide to reset the program if the parameters no longer match those
  for the current program
* fix failure to update check-boxes for toggled plugin parameters when their
  parameters are changed by program changes