Start revamp of PID implementation/usage

Because the GEFS PID controller is actually incorrectly implemented,
start work on redoing it and also stop making the results dependent on
arbitrary speed ratio which makes it difficult to set limits on PID
controller.
Minor preparations/reorganisation/cleaning

Prepare for Greasemonkey support, clean up folder structure, named
folder, move binary zip files out of folder (yet to think of structure
to move .crx files), clean up unnecessary folders.
Separate plugins into different repositories

This repository has been forked from the gefs-plugins repository, but
will now only house the Nose Wheel Steering plugin, so that we can
implement versioning and handle development better. Autopilot++ will
remain in the gefs-plugins repository for now, but it might move
elsewhere in the future.