Create a list of example printhead setups

[lostapathy]

With the proliferation of various extruder, aluminum parts, and hotend combinations, it's gotten to where it's fairly complicated for new users to collect all the correct parts for their build and successfully assembly.

We could create pages with documentation on individual setups, and then add an index page listing them. Each such setup needs to include specific, reproducible descriptions of aluminum parts and direct links to specific stl files for printable parts. Just linking someone to a thingiverse page with 15 files (of which they need 2) won't be enough to prevent further questions/mistakes/frustrations.

Done well, this should make supporting new users a lot easier than what is involved now.