improvements to ScalarEq, EulerEq, SRHD

Accumulated various changes

• draft for 2d SRHD evolution
• rework ScalarEq 1d to use new broadcast routines
• use force=true on callbacks before evolution to make sure initial data is outputted
• updated ref tests because of previous point
• rework EulerEq and fix bdry conditions to be able to evolve sod shock tube test with entropy viscosity