Export document options to musescore (#768)

* start on doc exporter

* add more settings

* refactor for less duplication

* add barline prefs

* wip

* wip

* wip

* wip

* wip

* wip

* add xml types to gitignore

* recover correct gitignore

* wip

* settings basically complete

* refactor UI

* start implementing batch processing

* wip: files being listed

* wip all but the loggin

* ready to go, but depends on RGP Lua 0.75

* working

* refinement

* fixes for Windows issues uncovered

* fix up path delimeters to avoid doubles

* fix issues encountered with directory cruft on the disc.

* wordsmithing

* refinements

* update menu text

* status added

* Added separate menu options

* finished touches to get working on Windows

* bugfix

Author: rpatters1