Tie: add some C++ rigor and concision (issue 252230043 by address@hidden)

[nine . fierce . ballads]

Reviewers: ,

Description:
I wanted to see how Tie would look with instance methods instead of
static methods.  I'm looking forward to hearing your opinions.

I recommend starting with tie.hh.

There is no tracker for this.  It's not fully baked and it won't apply
to master anyway.

Please review this at https://codereview.appspot.com/252230043/

Affected files (+86, -67 lines):
  M lily/accidental-engraver.cc
  M lily/completion-note-heads-engraver.cc
  M lily/include/tie.hh
  M lily/include/tie-column.hh
  M lily/tie.cc
  M lily/tie-column.cc
  M lily/tie-engraver.cc
  M lily/tie-formatting-problem.cc
  M lily/tie-specification.cc