The term "Defaults" is not clear enough and looks like it may be
redundant with the "Factory Defaults" button. Let's try an alternative
"Save Settings" and "Load Saved Settings".
Also adding some tooltips.
And finally making the "Load Saved Settings" only sensitive if the "Save
Settings" button had been used at least once.
Add internal GimpProcedureConfig API to load/save "default values"
which are to be treated as if they were the hardcoded GParamSpec
defaults, but user-configurable. Also make all other load/save
functions available to other libgimp files.
In gimp_procedure_run(), if incomplete arguments are passed, don't
just complete them with the GParamSpec defaults, but look up the
user-saved defaults and use them if they exist. This happens before
everything else and brings back the PNG export feature of using
user-saved defaults also in non-interactive mode (but for all
procedures not just PNG export).
In GimpProcedureDialog, add "Load Defaults" and "Save Defaults"
buttons, they are the only way of managing the user-configurable
procedure defaults.
When clicking "Reset", show a popover with the reset options "Initial
Values" and "Factory Defaults".
