[Users] Make "rewrite" branch of McLachlan the default

I believe the "rewrite" branch of McLachlan is sufficiently stable and accurate to become the master now. The code is significantly cleaner and easier to understand, and it has (since I've been using it myself for some time now) also some features and corrections that may be desirable to have.

I suggest to make this the default now. I would give a brief presentation on one of the coming Mondays explaining the design choices and the differences, and after some brief testing we would switch over.

-erik