Simplified version of Trevor Daniels' SATB framework. (issue 38720045)

[tdanielsmusic]

Thanks Devon - there's a lot in here that potentially
is an improvement, but also some things that will need
further work.  For example, a quick test of an existing
file of mine which used S-A-T-B.ily, placed the lyrics
above instead of below the staves.  I'll need to play
with it a bit more to see if there are any other
problems.  It also seems to have only one line of
lyrics in the 4-staff layout rather than two or three
(needed for translations and/or phonetics), unless I've
missed something.

What we lose with this approach is transparancy.
With straight Lily code, the more adventurous users
could adapt the template to suit their personal
preferances.  With this, only Schemers can.  But
as that wasn't the primary intention, it's not a
strong point against.

So, give me a day or two and I'll respond more
fully.  Hopefully we can converge on a mututally
acceptable solution.

Trevor


https://codereview.appspot.com/38720045/