Made motor lugs disable-able

See merge request !149

Fixes for travel case

See merge request openflexure/openflexure-microscope!153

I've removed all reference to GNU Make from COMPILE.md, and added a mention of
virtual environments (which are now git-ignored)

Fixed offset causing tools to attempt to print at different heights

See merge request openflexure/openflexure-microscope!154

Build instructions update

See merge request openflexure/openflexure-microscope!156

* Now links to the correct STL download location
* Clearer instructions for motor board
* I no longer use "firmware" as this was confusing people - we refer
to the Arduino sketch and the bootloader.

Fixing the hole spacing for the sangaboard

See merge request openflexure/openflexure-microscope!150