Issue 3635: Doc LM: Improve the explanation of 'force-hshift

  Add an explanation of the 'horizontal-shift property

  Expand the explanation of the 'force-hshift property

  Make the example of using the 'force-hshift property
  more transparently clear.
ledger-lines: horizontal space only when present
spacing-options: clarify documentation
springs: comment and typo
note-spacing: stretch somewhat uniformly

Start with a basic spring based on the note duration, and apply optical
corrections to that.  This results in more consistent springs thus more
uniform stretching in polyphonic situations.
note-spacing: let compressibility be uniform; issue 3304

Comments implied that half the width of accidentals, etc., was added
to the ideal spacing between notes, but in fact only compressibility
was affected.  The non-uniform compressibility caused note-spacing
to become non-uniform when the lines were compressed.  For example
A sequence {\stemUp a a d a] would have the head of the D tuck under
the preceding A.

This commit keeps spacing uniform on compressed lines until objects
come within padding of each other.
Revert "Prevents dynamics from colliding with cross-staff stems."

This reverts commit 3bcfd69d91f52f70598f73719fbed7aa6eea8ad3.

Conflicts:

	input/regression/dynamics-avoid-cross-staff-stem.ly
	lily/include/interval-minefield.hh
	lily/include/self-alignment-interface.hh
	lily/interval-minefield.cc
	lily/new-dynamic-engraver.cc
	lily/self-alignment-interface.cc
	scm/define-grob-properties.scm
	scm/define-grobs.scm
	scm/output-lib.scm
Doc: NR Tidy up of A4 - fretboard diagrams

Removed bar numbers - inappropriate for this section

Added an @appendixsubsec for each of the three pre-defined
fretboard instruments (Guitar, Ukulele and Mandolin) so as
to make it easier to find in the index but also to break up
the apparent 'wall' of fretboard diagrams when viewing the
Appendix.
Doc: NR add \chord to examples in A2

Issue 3755

Added new column to show a working example (also useful for Blind composers)
Minor layout quibbles with @multitable means using the @* (forced break)
for TexInfo commands - not strictly LP doc policy - to enhance clarity

Reduced the line-width slightly of the @lilypond examples simply to
help accommodate the extra column
Doc: NR improve example of \accepts

Issue 3641

Improve example given in NR 5.1.7
Issue 3773: Add Changes entries for bare rhythms and \beamExceptions
Release: bump VERSION_DEVEL.
PO: update template.
Release: update news.
Add version to make-relative-copies regtest for GUB build
Add version to make-relative-copies regtest for GUB build
Add version to satb.ly for GUB build
Add version to satb.ly for GUB build
CG: remove obsolete git info

...most of these istructions were valid for git version ~1.5;
nowadays working with git is much simpler.
CG merge duplicated sections about conflicts and branches

* merge 'resolving conflicts' with 'merging conflicts'
* merge 'Organization of remote branches' with 'Other branches'