* lily/tie-column.cc (set_directions): set directions only once.

* lily/tie-column.cc (set_directions): set directions only once.
(add_configuration): new function.

* lily/tie.cc (set_control_points): new function

* lily/tie-column.cc (new_directions): new function.

* ly/music-functions-init.ly: set 'pitch property
iso. trill-pitch. This makes \relative work with \pitchedTrill

* lily/tie.cc (get_configuration): new function. Don't generate
control points, rather, generate configuration.
remove head-pair property.

* lily/include/tie.hh (struct Tie_configuration): new struct.