Add a STATE_HARMONY_FIGBASS_EDIT state

HARMONY and FIGURED_BASS editing shares the generic STATE_TEXT_EDIT state. This causes shortcuts for HARMONY and FIG_BASS which are characters to be 'eaten' while editing other types of Text.

The branch adds a STATE_HARMONY_FIGBASS_EDIT, for actions specific to them, making any character used their shortcuts available while editing other types of textual elements.