Align metronome mark at time signature or first musical element. Fixes #684. (issue1579041)

[n . puttock]

Hi Jan,

Have you checked what happens with full-bar rests?

I haven't tested your patch, but it's similar to the one I posted, which
suffers from invisible tempo marks at full-bar rests.

Cheers,
Neil


http://codereview.appspot.com/1579041/diff/2001/3001
File lily/metronome-engraver.cc (right):

http://codereview.appspot.com/1579041/diff/2001/3001#newcode78
lily/metronome-engraver.cc:78: == text_->get_property_data
("break-align-symbol")))
should be break-align-symbols (which complicates it a bit)

http://codereview.appspot.com/1579041/show