Eliminates the Hara_kiri_engraver. (issue 7061062)

[mtsolo]

Reviewers: ,

Message:
This doesn't crash in the test case Keith proposed:

\new StaffGroup \with { \RemoveEmptyStaves
 }  << { b1 b1 b1}
       { b1 b1 \break b1 } >>

Description:
Eliminates the Hara_kiri_engraver.

Uses a haraKiri context property in the Axis_group_engraver to
acheive the same functionality.

Please review this at https://codereview.appspot.com/7061062/

Affected files:
  M lily/axis-group-engraver.cc
  D lily/hara-kiri-engraver.cc
  D lily/include/axis-group-engraver.hh
  M lily/include/lily-proto.hh
  M ly/context-mods-init.ly
  M ly/engraver-init.ly
  M scm/define-context-properties.scm