FluxCorrect tests

Tests for FluxCorrect method. This currently runs a 3D simulation with a pure-hydro inclined entropy/contact wave and checks how well the various fields are conserved.

inclined_contact_smr_ppm

Integrates the entropy/contact wave using the PPM method. This effectively uses static mesh refinement.

inclined_contact_smr_vl

Integrates the entropy/contact wave using the VL+CT method in hydro mode. This effectively uses static mesh refinement.