Resolve "keama-leases step 1: move the source code"

This MR imports keama-leases from its own repository. This was developed in a new repo, so merging two unrelated histories. I've rebased the commits on top of keama master, so it looks more or less as usual.

There's quite a few leftovers that I'm not sure what to do (like the HTML+PHP script to run simple gui for the keama-leases). I think it's useful to keep it around for a while, until we integrate keama-leases with keama UI that we have.

Closes #53 (closed)