Blender Git Loki

UI: Modifier Panel Header Improvements

This includes a few improvments:
1. Always expose delete. This is the button everyone wants the most,
it makes a lot of sense to expose this.
2. Improve "name hiding capability." Basically always align the mode
buttons to the right, and count their number to see if the name fits.
3. Aligns more items, to look better, save space, and make the whole
header seem more grouped.
4. In my tests the "switch contexts" button never coincides with the
delete button, so they share the same space.

Differential Revision: https://developer.blender.org/D8037