Color and/or parenthesize single dots in fret-diagrams (issue 102450043 by address@hidden)

[thomasmorley65]

Reviewers: ,

Message:
Please review

Description:
Color and/or parenthesize single dots in fret-diagrams

Issue 2752

Makes it possible to color and/or parenthesize single dots in
fret-diagram-verbose

Introducing two properties for use in fret-diagram-details
 - fret-label-horizontal-offset
    affecting the fret-label-indication, like the existing
    `fret-label-vertical-offset'
 - paren-padding
    affecting the padding of the parenthesis

Extending relevant reg-tests.

Documenting it in NR, fretted-strings.itely

Please review this at https://codereview.appspot.com/102450043/

Affected files (+233, -51 lines):
  M Documentation/notation/fretted-strings.itely
  M input/regression/fret-diagrams-dots.ly
  M input/regression/fret-diagrams-fingering.ly
  M input/regression/fret-diagrams-fret-label.ly
  M scm/define-grob-properties.scm
  M scm/fret-diagrams.scm