Instances tab: List named styles from STAT table

[davelab6]

At the moment, the Instances tab lists the fvar named styles:

Samsa Inspector UI shows these in the 'Instances' panel.

However, Samsa also supports the STAT table, which has more sophisticated ways to provide named styles, including per-axis names that get combined. The Samsa Inspector UI is an early consumer of STAT named styles, in the STAT panel. While this UI is a bit overly nerdy, I think it is entirely appropriate for an inspector. This plugin can simplify a bit.

The Recursive font is a good example, that shows how 2 axes (slant and cursive) are combined in a single STAT table dropdown: