Improve parametric axis ordering

Following #335 and #340 I also want to request to improve fvar axis ordering, by using this order:

1. Optical Size
- absolute first, as this affects everything dramatically, and is a key concept that all designers ought to become aware of
2. User axes
- registered first group with some exceptions
- first, weight, because this is the #1 style variation used to structure typography
- second, grade, which always follows weight since it is used to finesse weight
- third, width, because this is the #2 style variation used to structure typography
- forth, slant
- other unregistered axes
- first, unhidden axes, alphabetical
- second, hidden axes, alphabetical
3. Parametric axes
- first, opaque
- first, parametric thick stroke (XOPQ), for same reason Weight is first user axis, also because its first in cartesian order
- second parametric thin stroke (YOPQ), as this is a more subtle way to finesse weight
- transparent second
- first, XTRA, cartesian
- second, Y Transparency bundle:
- YTUC, because cap height is most useful to adjust in typography due to ALL CAPS often needing special attention to look good
- YTLC third, because x height is useful to adjust in typography and its primarily shaped by this parameter, but others are needed
- YTAS forth to go with lowercase,
- YTDE fifth to go with ascenders, but as they are often less deep than ascenders are tall
- YTFI sixth because its more rare to adjust these