Let \afterGrace start a Bottom context

Let \afterGrace start a Bottom context

Previously, an \afterGrace as the first expression of music outside of
an existing Bottom context caused quite weird results.


Also contains commits:

with-music-match: lists should match completely

Previously music properties that were matched to a list of wildcards
could contain fewer elements than the list they were matched to,
leading to an error when the wildcard variable was being assigned to.

Now the list lengths have to be matched exactly: a shorter pattern
than the actual list length of the matched property cannot match any
more.


Fix \displayLilyMusic \partcombine...

Strictly speaking this oversight in issue 4356 did not actually
manifest itself as a bug because of another bug masking it.

[lemzwerg, 2017-03-01 05:17:17]

LGTM