Improved AssistantComposer reverting.

Bug fix: the FormsThatNeedReview and
ConfirmedForms lists are now cleared on revert.
Also: removed the unnecessary reload after save
all. This was no longer necessary after the revision
of reverting in the previous commit.
When a PaletteChordForm is open, disable all

other visible forms. When the PaletteChordForm
is closed, re-enable them again.
PaletteChordForm now returns correct strings

The returned strings now contain separators
consisting of  a comma and two spaces (instead
of the erroneous comma and one space).