Bar lines of newly inserted or appended measures should not be 'generated'

There is no evident reason for new measures to have a 'generated' bar line. If a bar line is 'generated' will loose most of the user changes on save and reload.

- `Measure` c'tor defaults to `_endBarLineGenerated = false`
- `Score::rewriteMeasures()` and `Score::insertMeasure()` create measures with non-generated bar lines.
- Added tests.