SSR Relay mount

Mounting bracket for three Solid State Relays, one with heat sink attached.

- All holes are M4
- Knockouts for improved cooling of non heat sinked relays (also doubles as support).
- Mounting holes spaced to fit 2060 aluminum v-slot extrusions.

27Oct2017 - Fixed spacing on heatsink holes. Increased diameter and depth of counter sinks. Modified knockouts to (hopefully) be easier to remove.