Glyphslib

- Generate brace layer name automatically if the user added a brace layer outside Glyphs and forgot to insert the special glyph lib key storing the original brace layer name as used by Glyphs (522).
- Support `public.skipExportGlyphs` lib key for storing export flags: the export status is no longer written to the glyph lib key `com.schriftgestaltung.Glyphs.Export`, but to the UFO and Designspace lib key `public.skipExportGlyphs`, following the addition of it to the UFO specification.
Needs ufo2ft 2.8.0-b1 or above to honor (519).
- Support glyph lib key `ComponentInfo`. It's used to preserve which non-default anchor a mark is attached to when automatic alignment is active (can be important in e.g. Vietnamese composites) (521).

- Reverted PR 451 (released in v3.3.0) after discussion in 483.
This restores the original behaviour from v3.2.0: that is, only when `Axis Location` custom parameters are not used (i.e. defining user-space locations for each master) -- and therefore, the instances' locations are considered when building DesignSpace axes --, then for the `wdth` axis, the user-space (i.e. fvar) coordinates are assumed to be the same as the internal design-space coordinates, and the OS/2 widthClass is **not** used to map from user-space to internal design locations. Hence there are no `<map>` elements for width axis in the generated DesignSpace document, and thus the variable font's ``avar`` will **not** contain any mappings for `wdth`.
The change will be reintroduced in a way that doesn't break existing workflows relying on the previous assumption.
- Generate brace layer name automatically if the user added a brace layer outside Glyphs and forgot to insert the special glyph lib key storing the original brace layer name as used by Glyphs (522).
- Support `com.schriftgestaltung.Glyphs.ComponentInfo` glif lib key, used to preserve which non-default anchor a mark is attached to when automatic alignment is active (can be important in e.g. Vietnamese composites) (521).

- Opportunistically round coordinates and other values of the form `x.0` to `int`
- Round-trip the filter `com.github.googlei18n.ufo2ft.filters`. It will show up in the custom attributes of masters, where Glyphs ignores it
- Try harder to derive (sub)category for ligatures
- Make use of the OS/2 width class value when determining where on the width axis a Glyphs master is
- Remove 'build_instances' from `__all__`; fixes `AttributeError` when doing 'from glyphsLib import *'

Updated GlyphInfo*.xml files to state of Glyphs 2.6.

Also refer to the beta notes.

- Master, Custom parameters, "Axis Location": run `int()` on location to work around a bug in Glyphs.app that sometimes stores the number as a string instead of an int.
- Added CLI option `--no-store-editor-state` to not store state like the currently opened glyph tabs ("DisplayStrings"), as this easily leads to gratuitous merge conflicts.
- `build_masters` will now correctly store masters on disk. Before, source layers would overwrite the full master UFOs.
- Support automatic generation of bracket layers. They are extracted into freestanding glyphs in glyphs2ufo and back again in ufo2glyphs. Only the foreground layer is currently preserved!

UFO2Glyphs: Ensure color tuples consist of integers in Python 2.