Extended c270 mount to cover pcb and added backshell with cable grip

TODO:

• Print and check assembly on camera
• Put in a microscope and check it doesn't obstruct range of motion (may do where the cable comes out) - In rev2 and rev3 it does not give any more obstruction than the camera board itself. The main stage legs touch the sides of the camera board before the end of motion towards the x or y actuator.
• Update all renders
• Update instructions
• #386 (closed)
• #413 (closed)

NB: This change also affects the c270 RMS optics modules. (closes: #386 (closed) and #413 (closed))

Rev 3 (or probably 6):

See below for earlier versions

The cable exiting below the board makes fitting the module a little harder, you need to deliberately hold the cable to the side. This will need to be in the instructions.

Everything rounded (and some internal changes).
Never use one that is printed in white 😄

The cover extends up to the camera platform, where it sits on a little shelf to hold it in place.

I think this is now the right shape.

Rev 2:

See below for Rev 1

Rev 1:

This held the camera cable nicely using the e-clip to maintain position. But the cable protruded out of the microscope which was bad. Also assembly was quite fiddly

Render:

Photos: