CMM at the end of the pipeline + sparse code refactoring
A new BPC checkbutton has been created in 'Preferences/Color Management'
and in the ICM tool. Better hanbling of widget sensitivity of the output
profile / gamma part of the ICM tool.
Most conflicts seemed to be simple enough. There were a lot of `append_text` to
`append` conversions for `Gtk::ComboBoxText`. The `PopUpCommon` class also saw
a lot of changes with non-trivial conflict resolutions.
