With lung cancer simulations table S3 defines the column to use for table S4
(cf. ../documentation/simrisc/supplementary.odt). The member 'loadS3' loads
table S3 into the ProbGroup::Vector d_s3.

Survival's constructor calls loadS4 to store the a..d parameter means and
std.devs in d_vsdMatrix.

When initializing a case Tumor::characteristics() defines the tumor diameter,
which value is then passed to its d_survival object's computeAD() member. This
member does nothing for breast cancer simulations, and determines the S4
column to use for lung cancer simulations.

The required probability is a random value returned by Random::uniformCase().

Once the S4 column has been determined, 'varyLung' is called to compute the
randomly varied a..d parameters of that column.

Survival [0..3] values are then used by Tumor to compute its functions F, Q
and Z.
