Boundary condition for hydrostatic pressure

[wortiz]

Developer: D. Hariprasad, December 2014
Description: Specifies pressure as P = P_0 + rhogx where rho is a variable
density and the user specifies P_0.
Example: BC = FLOW_PRESSURE_VAR NS 1 0

Capability: Galerkin least-squares continuity stabilization
Developer: D. Hariprasad, February 2015
Description: Adds a Galerkin least-squares stabilization term using the residual
of the continuity equation for incompressible or steady-state compressible
flows. This should help with high Reynolds number flow. Similar to the
Pressure Stabilization already implemented in Goma. See Franca and Hughes 1988
for an abstract discussion of the method or Forster, Wall, and Ramm 2010 for a
Navier-Stokes based discussion of the method. The choice of a local or
global stability parameter is left to the user.
Example: Continuity Stabilization = local