Glyphslib

Testing automatic deployment via Github CI.

- Added support for "Axis Mappings" font custom parameter (618, 568).
- Accept floats in brace layer name definitions (616).

Fixed two issues with anchor propagation in composite glyphs (617, googlefonts/fontmake682).

1) marks that are in turn composed of other marks (e.g. "shadda_fatha-ar") didn’t receive propagated anchors at all. A solution was already developed in ufo2ft's `PropagateAnchorsFilter`, so Yanone ported that piece of code over here.
2) ligature anchors (top_1, top_2 etc) weren’t correctly propagated when composed of base glyphs and a mark (e.g. "lam_alefHamzaabove-ar"). To fix that, we now check for marks attached to a named `GSComponent.anchor` (stored in UFO as `Glyph.lib['com.schriftgestaltung.Glyphs.ComponentInfo']`), and adjust the named anchor’s position by the component transformation.

* Decompose background layer components due to tricky reasons, see 610.
* Added a pen and `draw` and `drawPoints` methods to Layer, Path and Component classes.

- Make sure we don't end up with a Designspace with empty axes, even when there is only a single master at default location (googlefonts/fontmake644).

Make sure the lastChanged timestamp is not written to the UFO when not wanted ("Disable Last Change" custom font parameter is true).