Tune the automatic placement of markings

[frmatthew]

Right now there is no intelligence about marking placement based on neume type. So, if a horizontal episema is added to the first note of a podatus, by default the marking hint will be "Above", and thus look totally wrong. Likewise, a podatus and clivis with morae on the notes will look bad, depending on line placement, etc.

The neumes classes should handle some basic logic at least to try to intelligently place the markings.

[frmatthew]

Commit df96608 improves upon this, but there's still a lot of work to be done here...