Create Bracket class (issue 314610043 by address@hidden)

[david . nalesnik]

Reviewers: ,

Message:
Please review.  Thanks!

Description:
Create Bracket class

Code involving brackets suffers from two confusing
organizational issues:

(1) Tuplet_bracket::make_bracket is used to create brackets
for a number of grobs: BassFigureBracket, HorizontalBracket,
OttavaBracket, PianoPedalBracket, VoltaBracket, along with
TupletBracket

(2) Methods belonging to Horizontal_bracket are used to draw
both horizonal brackets (HorizontalBracket) and vertical
brackets (BassFigureBracket)

To remedy this, a new Bracket class is created.

This new class contains the old Tuplet_bracket::make_bracket,
Horizontal_bracket::make_bracket, and
Horizontal_bracket::make_enclosing_bracket.

These methods have been renamed to clarify their purpose.

Please review this at https://codereview.appspot.com/314610043/

Affected files (+199, -178 lines):
  A lily/bracket.cc
  M lily/enclosing-bracket.cc
  M lily/horizontal-bracket.cc
  A + lily/include/bracket.hh
  M lily/include/horizontal-bracket.hh
  M lily/include/tuplet-bracket.hh
  M lily/ottava-bracket.cc
  M lily/piano-pedal-bracket.cc
  M lily/tuplet-bracket.cc
  M lily/volta-bracket.cc