treewide: modules -> profiles, separate dirs, list in README (#29)

Enforce proper naming: all paths are lowercase and hyphen-separated,
if there's a line of models (aspire, macbook-pro, thinkpad) it becomes
a subdirectory. Documentation for profiles is moved to README files in
respective directories.

Add an Org mode table that lists all available profiles and their paths.

Instead of fetching repo locally, use a Nix channel. Making hardware
profiles read-only should improve quality and amount of participation
long-term.