New scripting functions: SelectGlyphsSplines, SelectGlyphsReferences, ChangeWeight, and "Class" tag to GlyphInfo()

New native scripting functions added: SelectGlyphsSplines(), SelectGlyphsReferences(), ChangeWeight(), which parallel the commands available through the graphical UI for use in scripts.  (ChangeWeight is called Embolden in the UI).

The glyph class (automatic, none, base, ligature, mark, component) is now available through GlyphInfo() using the "Class" tag.

Documentation is updated to reflect these additions.