Code points should be editable

[ollimeier]

Code points are currently not editable:

[justvanrossum]

Solving this requires some rethinking/reworking of the backend protocol (see protocols.py). In Fontra, the glyph object is not in charge of its code point(s), but these are managed by the glyphMap object. (The front end also maintains a characterMap object, the opposite of glyphMap.)

So we have a bit of an impedance mismatch between the UFO model and Fontra's model, and the backend API is a bit confused in this respect. For example, we read the code points via getGlyphMap(), but we write them via putGlyph()... This is not ideal of course, and needs a bit of redesign.