Reroutes: Fix shift-drag output link(s) removes all reroutes

[webfiltered]

Example:

lose-reroutes-on-move.mp4

[LukeG89]

It's not just the shift-drag, it's also when you switch inputs (or you just disconnect the input e reconnect it).
And when you switch input from a second link of the same reroute, the connention is made between the nodes (similar to the fast connection bug)

Switch-Disconnect-Input-Reroutes.mp4

[webfiltered]

Yeah, but look at the bright side, if you do the input link thing without dragging it anywhere it, the reroutes don't disappear!

This is a bit nastier than I thought. I'll get some fixes in soon.