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" (see the attached video) Basically always align the mode buttons to the right, and count their number to see if the name will fit.
3. Aligns more items, to look better, save more 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.

This patch *doesn't* do a few other things:

1. Give a tooltip to the icon with the modifier name when the name isn't shown. I was running into difficulties with removing the emboss in this case.
2. Add shortcuts to the modifier (see D8031)
3. Expose the "apply" button. I don't feel too strongly about this, but I don't want to force people to make the header too wide. One of the benefits of the new UI layout is that it works in a narrow region.
4. Get rid of / change the menu. The menu allows us to add more operators (see patch ...), and to access all modifier operators when the panel is closed.
5. Move the icon into the name field. Combining these two makes them seem more related than they actually are.
6. Change panel dragging. This is not related.