Material reorganization
Updates to the attribute organization, including
- Flatten material/phase properties
- Add "invariant-properties" group for density, reference_enthalpy, referenct_temperature
- Make shared properties now act as default properties (can be overridden in individual phases)
- Add support for Truchas specific_enthalpy_func and solid_frac_table variables
- Copy phase 1 properties to common group when adding 2nd phase
- Add "body" attribute and "Body" tab to subsume initial-conditions and material associations
- Refactor views to remove "Globals" and "Other" tabs with "Outputs"
- Update export scripts to match attribute changes.
- Add end-to-end test for new features (specific_enthalpy, solid_frac_table)