Seckit Cube endstop mounts for normal microswitch

Normally, the Seckit Cube has the x-axis endstop on the hotend. This makes it a tiny bit heavier, but also adds more wires to an already large bundle coming off the top of the hotend.

This moves the X-Endstop to the gantry and uses a light, flexible wire (headphone wire is what I'm currently using) to connect it, retained by a clip that fits under the linear rail.

These mounts also replace the tiny switches with standard microswitches. In addition to being more common, the larger switches have some extra room after they engage, which should help keep the hotend from banging into the endstop.