New bug label: engraving-nitpick

[Graham Percival]

I've added a new label for bug reports: "engraving-nitpick".  This will
be used for musically-simple examples that produce ugly engraving.  In
most (if not all) cases, these could be fixed with a few \override
commands, but these are IMO simple things that a user could reasonably
expect lilypond to handle beautifully by default.

I'm not expecting resolution of these items in the near future; some of
these could be unresolved for years.  I think it's still worth adding
them to the tracker, though.  I wasn't expecting any resolution to the
\mark problems (ie vertical skyline stuff) to happen for years, and I'm
amazed at the magic that Joe has worked.

For example,
http://code.google.com/p/lilypond/issues/detail?id=163

Cheers,
- Graham