Changes

Added pressure-saturation formulation to Porous media, added support in
PXResidual to upwind viscous fluxes individually for each equation, and
also the ability to turn off the lifting operator for selected
equations. PXCalculateResidual has some commented out code that can
modify the global residual vector and its jacobian, and print it to a
file if needed.

Added hook for passing in state gradient UX into inviscid flux routines
for all EquationSets, and also to return derivatives of fluxes w.r.t.
UX, modified PXResidual.c to handle convective fluxes that depend on UX,
added jump-flux stabilization term of 2-phase flow to inviscid routines
in the PorousMedia library and also to PXResidual.c, more unit tests for
PorousMedia

fixed uninitialized variable warning for clang

fixed memory errors, and added pointer to BCStateGradient function even
for Euler2d/3d equationsets

More bug fixes

Fixed unit test failure

added line-search to local solves, modified jumpflux stabilization for
two-phase flow, additions to residual vs update fraction output tool -
might fail unittests, committing as backup

added Buckley-Leverett equation to PorousMedia with Lax-Friedrichs and
Godunov numerical fluxes, added routines to support surrogate variables

Added knob file input for capillary model data

Bug fix for CutCell_rae2822_CHT

bug fix for uninitialized variable

More unit-tests to increase coverage

more unit tests

more bug fixes

memcheck bug fix