Restore old kOS versions (revert: "NetKAN available")

This reverts commit 8c1c6f1bb12079f33ec33c192efb4de775b8b488
as part of #53. We really do want to keep old metadata around
for the moment, both for old KSP versions and so poeple of the future
can choose to install older versions if they wish.

Unless I've missed something important here. Let me know if I have.