Open bc projected nodal gradient is not using specified user value

[spdomin]

Technically, the projected nodal gradient and bcs should be using the known value. This is currently only coded for pressure. However, other dogs such as velocity, tke, sdr, enthalpy, and species are using the current dof value.

For species, it can be more complex as we need a field for the current open bc species value.

This is probably not very serious of an issue, however, should be fixed.

[spdomin]

This is actually more complex... For example, at an open bc, the specified value might only be appropriate when there is entrainment into the domain.

Need to think more about this. Perhaps this approach should only be used at flux inflow and flux wall bcs.