Implement traction, pressure, flux BCs + source in input files

[Alex Tyler Chapman]

Some input files cannot run due to these boundary condition types not being implemented.

https://github.com/LLNL/serac/blob/develop/src/serac/physics/solid_mechanics.hpp#L322-L332

[Alex Tyler Chapman]

As well as "source" and "flux"

https://github.com/LLNL/serac/blob/develop/src/serac/physics/heat_transfer.hpp#L240

https://github.com/LLNL/serac/blob/develop/src/serac/physics/heat_transfer.hpp#L254