Added displacement distribution handling, a process similar to turning angles distribution.

It is intentionally called a displacement, instead of velocity, to stress the fact
that the class does not deal with time variable at all.

Added one more state handling of a real number generator (because of the disp. distro).

Added UseCorrectedUniformDistribution() for the turning angle distribution which
actually creates not uniform distribution, but after drawing random samples from it,
the produced distribution is some-what nearly uniform (quite unlike from the one
produced with UseUniformDistribution()).

Added RandomWalk::ReadyToStartSimulation() indicator for those who are not sure...
M    toolbox/randWalk.h


Adjusted to provide similar trajectory data as the real example.
M    toolbox/walks.cc