Freeflow/rans problem redevelopment

fixes #574 (closed)

• The isothermal-noncompositional tests all pass
• The only nonisothermal-noncompositional test passes (ni_ZeroEq). Set up tests for other models.
• The only isothermal-compositional test passes (2c_ZeroEq). Set up tests for other models
• The NCNI tests all pass.
• Update tests according to !1493 (merged) using the appropriate enable_if template arguments.

This can be merged when !1486 (merged), !1484 (merged), !1493 (merged) are merged.