Update SchumannR Romanzen to 2.18.2

Use StaffGroup instead of PianoStaff to facilitate 3rd "piano" staff
Move explicit breaks to a break voice to allow sizing distance between the first staff pair.

Romanzen is implemented in an LYS folder with a notes file and a separate file to implement letter and a4 formats. After this update the only difference between the 2 files is the setting to global-staff-size.