Add `layerName` attribute to the sourcedescriptor object
Read and write layerName.
Add a source layer test.
XXX this also disables the test_check() test for the moment because it generates odd results.
- if the axis value is missing in the neutral location, add the axis and value.
- if the values are different, then use the value from the neutral location as the axis default.
If there are no defined axes, use the available names from locations in the document. New axes are tagged with "_" as first letter. There is no guarantee that the guessed axes have the same dimensions as the originals.
- aims to do work the same way as mutatorMath.ufo.document
- generate all instances as UFO
- handle glyph masters, info, kerning, lib
More testing is needed.
- independent reader / writer object for designspace documents.
- imports and exports easy to subclass objects for instance, source and axis data.
- roundtrips
- intended to be compatible with use in MutatorMath, Superpolatpor and varlib.
