improve dragtag

[bob8677]

added alt drag to swap tags and control+shift drag to combine the shift and control drag (move all windows + follow) also made it so that you can start dragging while holding down a modifier key as well as adding the ability to do actions when clicking on other tags (and check modifiers).

Not sure if there is a better way to get what modifiers are held down other than XQueryPointer, I shouldn't have to get the mouse position to see keyboard modifiers.

Might be buggy, not sure