Make a "quick fix" doc for common errors (hints/tips for us) for each module

[bvoight]

This year, we had UNIX-I students clobber some files, and we forgot that we could curl/wget the files from github directly to replace them (it ended up being a huge time sink and headache to fix)

we should make a googlesheet or something which remind us where/how to get files like this, or if there are common mistakes how we end up fixing them (quickly), so that we don't forget