Fix back compatibility wih 1.3 symbol names

Symbols names stored in 1.3 scores (or previous 2.0 scores) are not recognized and replaced by a default fall-back symbol.

Added a vector and a Sym static function for re-mapping of old names into symbol IDs.

Also fixed:

- renamed "mensuralProlation1...11" to names expressing the meaning of the glyphs (in SymId, Sym::symNames, Sym::symUserNames and .json files);
- some details in fonts/bravura/glyphnames.json;
- added several glyphs to fonts/mscore/glyphnames.json;
- corrected Sym::userName2id() to really return SymId::noSym on name not found, rather than -1.

NOTE: due to an oversight in my git workflow, this PR also includes the previous PR for reading back symbols from score files. Please advise if this is a serious problem.