Convert source from .glyphs to UFOs plus Designspace

The purpose of this MR is to port the Cantarell source from the proprietary .glyphs format to the open Unified Font Object (UFO) format for the masters and the Designspace format for storing variable font/interpolation information. These open formats can be read by more applications and have better compilation and processing libraries available, although both formats do have flaws.

In the process, I have added custom compilation scripts for making static instances and a variable font for more control and cutting down on dependencies (maybe).

Closes !6 (closed).

Todo:

• Check anchor propagation. We don't want it for non-letters like numero, but in e.g. ocircumflextilde, the anchors from the base o are propagated, but not from the combined diacritic circumflexcomb_tildecomb above it, which has no anchors propagated. Depends on a new release after ufo2ft 2.7.0.
• Clean-up spurious anchors in some currency symbols
• Convert all point coordinates with .0 at end to integers? Seems to be a glyphsLib thing.

Left for later:

• subs vs. sinf in features.
• Generate GDEF in the pipeline from GlyphInfo data?