Doc-fr: full update
Issue 346: monochord issues

This lets a reverse notehead at the stem start creep up closer to its
same-pitch unreversed partner in order to avoid a gap caused by notehead
slant.
Issue 4083: Implement \tagGroup command
Basic documentation for \tagGroup command
Add regtest for \tagGroup command
Refactor grammar, folding complex_music into composite_music
Refactor grammar, folding re_rhythmed_music into composite_music
Refactor grammar to give \addlyrics a good target to attach to

So far,

    \new Staff \new Voice { c1 } \addlyrics { Oh } \addlyrics { Ah }

was factored as

    \new Staff \new Voice { { c1 } \addlyrics { Oh } \addlyrics { Ah } }

which resulted in something like

   \new Staff \new Voice
     << \context Voice = "uniqueContext0" { c1 }
        \new Lyrics \lyricsto "uniqueContext0" { Oh }
        \new Lyrics \lyricsto "uniqueContext0" { Ah }
     >>

This made it impossible to work with the likes of

  \new Staff \new Voice \with { \stemUp } { c1 } \addlyrics ...

since the voice the lyrics attached to was always a new voice.
Fixing the grouping in the grammar is a first required step for getting
this under control.
Fix bugs preventing \addlyrics from finding an existing context to attach to
Give \addlyrics the power of christening the associated context

With

\new Voice \with { \stemDown } { c1 } \addlyrics { Oh }

as opposed to

\new Voice = "upper" \with { \stemDown } { c1 } \addlyrics { Oh }

\addlyrics created its own context (consequently not using \stemDown)
since it had no context name for the Lyrics context to attach to.  In
this case (namely being preceded by an unnamed new Voice context), it
will now give a name to the context itself.
Convert \new Staff ... \addlyrics into \new Staff \new Voice ... \addlyrics
Add regtest for issue 4096, \addlyrics using existing contexts
Merge branch 'issue4096' into HEAD
Derive melisma_busy state from child contexts when available
Allow associatedVoice to be of different type than Voice
Revert "Convert \new Staff ... \addlyrics into \new Staff \new Voice ... \addlyrics"

This reverts commit 76f256075f0a4f481d7e11c19dd55ab09030fe5b.
Allow \addlyrics to work with arbitrary contexts
Add regtest for \addlyrics on Staff context
Merge branch 'issue4097' into HEAD
Release: bump VERSION_DEVEL.