Instructions for different microscope versions

[gpereyrairujo]

In case there are different versions of the microscope (as it was during the GOSH workshop), the documentation should have a clear reference to the different kits/versions available, so as to be sure of the parts needed for each version, and the associated assembly steps.

[rwb27]

Bonus points for integrating this with a build script (#22) so we generate a BOM, DocuBricks documentation, and a folder of STL files for each possible set of options. In the future we might have to do this on demand, from a pre-compiled library of STLs and XML fragments.

[rwb27]

Since swapping to Markdown instructions, hopefully this is clearer - though still not perfect. Once we build the instructions and add an automatic BoM, customising them should get easier.