Adjust camera cover around screws and for connector space

This MR:

• Increases the counter bore radius for the screws
• Increases and elongates the structure around the counterbore to ensure printing (does not interfere with components)
• Slightly decreases the counter bore depth so that the clearance hole prints fully
• Increases the radius of the clearance hole so the screws moves through freely
• Modifies hole_from_bottom utility so that the number of layers can be set
• Sets the number of layers to 2 so that the final clearance hole is an octagon.
• Rotates the clearance hole structure to improve the print bridging
• removes the chamfer on the back, the new cover is less long and has a cut out for the connector

Note that the counter bore depth is not the whole height of the pan head. The rounded back protrudes, but this should be fine.

Closes #210 (closed)

/cc @williamwadsworth