This commit introduces two functions,
LogiHEAD::pvtModel()
LogiHEAD::saturationFunction()
that set LOGIHEAD flags pertaining to a subset of activated
features. In particular, we add the ability to control whether or
not a particular run applies to a live/dead oil case, a wet/dry gas
case and/or whether or not a dead oil case is specified in terms of
constant oil compressibility (PVCDO keyword). Saturation function
flags identify attributes of end-point scaling and directionally
dependent and/or reversible relative permeability functions.
Add unit tests to exercise these features.
