Need to be able to reorder components

[justvanrossum]

This is quite important for complex glyphs, as is common in CJK design.

Relates to #1117.

Visually this could be a list with an item per component, where each item shows the whole glyph and the component highlighter. Reorder by drag and drop seems like an obvious choice.

[justvanrossum]

Glyphs has this:

[ollimeier]

I would expect, that reordering components would work in the glyph info sidebar via dragging and dropping the components into the right order, similar to how you implemented the reordering of axes: