Unifi Cloud Key rackmount module

A remix of one of russross's modular Raspberry Pi rackmount sleds and bellingeri's rackmount Unifi cloud key holder:

- https://www.thingiverse.com/thing:4125055
- https://www.thingiverse.com/thing:4609160

Next versions and plans include:

1. Using the sled mount instead of modifying the rack unit
2. Moving to 2u format and putting a front keystone jack (requires significant reworking of the 2u modules)

Also planning on:

1. PiKVM and EZCOO KVM
2. Arris SB8200 cable modem
3. Meteobridge Pro