MultiDock 2 USB panel-mount socket adaptor

Adaptor plate to use a generic panel-mount USB socket in a Griffin MultiDock 2 (as a replacement for an original riser card). This was designed as part of the [STFDock project](https://hackaday.io/project/21320-stfdock/), which involved turning a MultiDock 2 into a self-contained (just supply power and plug devices in) OpenSTF device lab.

The panel-mount USB sockets I used required some trimming with a sharp knife in order to account for the raised section which corresponds to the thin edge which slots into the MultiDock. The raised section provides adequate support to counter the loss of material, especially when the socket is screwed on to the adaptor plate.