MoveHandler: Ignore unused mods for determining the MoveModes

[Leleat]

The default move mode is activated when no modifer key is pressed. That may be to restrictive however because the Super key is used when the user wants a window to span multiple tiles. So instead now fallback to the default move mode, only if used modifier keys aren't pressed.

Fixes https://github.com/Leleat/Tiling-Assistant/issues/339