v4.0.0

Major new release since worldfile syntax and API have both changed due
to a new unified ranger model. Laser model is now deprecated in favour
of the ranger. This follows a similar change in Player 3, where laser
interface support was deprecated but still in place due to lack of
Stage support. This release fixes that.

Also includes many bugfixes, a much improved build system and some
performance enhancements and documentation improvements.