Do not force repeat bar lines to "generated" status.

Dropping a repeat bar line (of any kind) or splitting an end-start-repeat bar line with a line break changes the status of the involved bar lines to "generated". This prevents any future edit (span, visibility, colour, ...) to be saved and to stick.

Fix: The current generated status of the bar line is used instead.
Added test.
Merge pull request #599 from mgavioli/repeat_barlines_not_forced_to_generated

Do not force repeat bar lines to "generated" status.