fix warning reg. unused variable

a leftover from 07abb7f
fix #25600
rename enum Dynamic::DynamicType to Dynamic::Type
move enum DynamicRange to Dynamic::Range

needed to make it available to the Plugin framework
change enum class SymId back to int

the memory saved is not worth the performance penalty
move enum Placement to Element::Placement

needed to make it available to the Plugin framework
move ElementType to Element::Type

needed to make it available to the Plugin framework
move SegmentType to Segment::Type and make int again

needed to make it available to the plugin framework
and the memory saved is not worth the performance penalty
rename AccidentalRole and AccidentalType to Role and Type
rename Hairpin::HairpinType to Hairpin::Type

and register Hairpin::Type, FiguredBassItem::ContLine and
Lyrics::Syllabic, which seemd missing.
Also fix registration of Element::Type and Segment::Type to what they
had been before.
rename LayoutBreak::LayoutBreakType to LayoutBreak::Type
rename Trill::TrillType to Trill::Type
move GlissandoType to Glissando::Type

needed to make it available to the plugin framework
some cosmetic changes to plugin documentation
move MarkerType to Marker::Type

needed to make it available to the plugin framework
move ValueType to Note:ValueType

needed to make it available to the plugin framework
move NoteHeadGroup to NoteHead::Group

needed to make it available to the plugin framework
move NoteHeadType to NoteHead::Type

needed to make it available to the plugin framework
move OttavaType to Ottava::Type

needed to make it available to the plugin framework
move VoltaType to Volta::Type

needed to make it available to the plugin framework