Only one PaletteChordForm can be open

A PaletteChordForm will now only open if
there are currently no other ones open.
This is in preparation for cleaning up
saving.
N.B. PercussionPaletteForms are only
partially complete...
Cleaned all help texts and tab orders

in Palettes project.
Restructuring Saving: OrnamentSettingsForm

beginning to implement a new saving
strategy for .mkss files.
The OrnamentSettingsForm is complete, but
otherwise the following restructuring is still
incomplete.
Each of the Assistant Composer's subsidiary
forms is going to be given an OkayToSave and
RevertToSaved button, implementing a new
.mkss saving strategy.
Each of these forms will manage its own 'saved
status', setting its title text accordingly.
Before the AC saves, it is going to check that
none of the forms' titles ends with a "*". If a
form's title does end with a "*", then the form
has to be reviewed, and either its OkayToSave or
RevertToSaved button has to be clicked to
remove the "*".
Restructuring Saving: PaletteForm

PaletteForm now conforms to the new strategy.
(see previous commit)
Restructuring Saving: DimensionsAndMetadataForm

DimensionsAndMetadataForm now conforms to
the new saving strategy (see previous commits).
Removed MIDI Percussion Forms

MIDI percussion can now be defined and tested in
normal palettes. Currently, the test buttons
automatically use channelIndex 9 on the Microsoft
GS Wavetable Synth, overriding the output device
set in Moritz' main form.
The MIDIPercussionHelpForm, which now contains
a longish comment, can now be opened from a
PaletteForm, when the new 'percussion' checkBox
is checked.
Also tested and working in PaletteChordForms.
Removed IPaletteForm interface

This was no longer needed.
New IRevertableForm interface

and new class RevertableFormFunctions
containing the functions necessary for
implementing it.
Implemented IRevertableForm for
DimensionsAndMetadataForm
PaletteForm, PaletteChordForm and
OrnamentSettingsForm.
TODO: implement it for
AssistantPerformerMainForm.
Reverting AssistantMainForm implemented

This reverts just the notation and krystals areas
of the form. PaletteForms, OrnamentSettings
and DmensionsAndMetadata must be reverted
individually.
Added the remaining Buttons to the
AssistantMainForm, but these are not yet
functional.
Continued work on AssistantComposerMainForm

There are now separate buttons implementing
IRevertable for the notation, krystals and
palettes panels. These currently work properly
with each other and with the form as a whole.
Revised the layout of the other buttons too:
RevertCompletely, ShowCheckedForms and
ShowUncheckedForms have not yet been
implemented.
The AssistedComposerMainForm_Activated()
event handler exists, but does not yet do
anything.
RevertEverythingButton implemented

in AssistantComposerMainForm.