[1.0] Key sig properties (w/ patch)
Purpose: Allows to set the following properties for each key signature change: a) whether to generate a courtesy signature or not, b) whether to display naturals (if any) in the key or not.
Applications: Composite scores with movements/parts/pieces in different keys can be kept in the same score, formatted as they were independent scores, but ensuring all the other settings are consistent; pieces can even share a page. Global courtesy key setting can be kept on to show courtesy key changes inside pieces.
Notes: Properties are set in the key signature contextual menu and written/read to/from the .msc? file.
A patch is attached; most of the code comes from the trunk; extensively tested with branch.