This new widget is much nicer, with proper label to document the GUI and
also with support to save files or create folders. It also has mnemonic
support and the label is put into the same size group as other so that
it's nicely aligned.
As a consequence, I remove bad support of object arguments with a GFile
value. People should just create proper GimpParamSpecFile arguments
(also GimpProcedure API now has a function only for such type of file
argument).
I also remove gimp_procedure_dialog_get_file_chooser() which was only
useful when we didn't know what action a file argument was for. Now it's
part of the param spec definition.
libscriptfu was updated too because SF-DIRNAME arguments don't need
special casing anymore.
Finally I change gradients-save-as-css to just make use of the new
automatic widget creation (more than 60 lines of plug-in code replaced
by… 0 lines because it's automatic!).
This whole commit is mostly a lot of code removal now that we have
proper automatization for file arguments! \o/
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