Add "color-profile-path" to GimpDialogConfig to remember the last-used
path in any profile chooser dialog.
Whenever a GimpColorProfileChooserDialog is created, call a new
gimpwidgets-utils helper function that connects to the dialog's "show"
and "response" signals and makes sure "color-profile-path" is set on
the dialog if it doesn't have a current folder already, and sets the
property back to the config object when a profile was actually chosen
from disk.
