Simplify instance naming in VF & separate family names in statics for new GF standards

[thundernixon]

New spec for naming variable instances in multi-axis family, and for naming static fonts in such a family:

https://github.com/m4rc1e/gf-docs/tree/f17762edf8cb92c98625e60d7620d00c4df2d7cc/Spec#supported-styles

In summary, this will likely require creating specific designspace files, then going from the Glyphs source to UFOs to build from there.