* scm/output-lib.scm (string-finger::calc-text): new function

* scm/output-lib.scm (string-finger::calc-text): new function

* lily/new-fingering-engraver.cc (add_fingering): refactor; make
generic for fingering & string number. Use for string-finger.

* scm/define-music-types.scm (music-descriptions): add StringFingerEvent

* lily/fingering-engraver.cc (listen_string_finger): new function

* scm/define-grobs.scm (all-grob-descriptions): add StringFinger

* scm/define-context-properties.scm
(all-user-translation-properties): add stringFingerOrientations