Start a test suite for class BlackoilPropsAd.

Relies on external data ("fluid.data") to describe the fluid model.
Merge remote-tracking branch 'atgeirr/master'
Expose 'param' and 'deck' in TestFixture.
All "parameter" values must be strings.
Default to using tables as-is.
Disable 'param' output for all test cases.
Add required fluid densities
Add test cases for density and water viscosity.

Currently, ViscosityAD fails due to missing pressure derivatives in
the viscosity primitives.
Ignore autosave files from Vim.
Moved spdiag out of an anonymous namespace.

It is a function meant to be called by clients, not an implementation detail.
Merge remote-tracking branch 'bska/master'
Updated for helper class name change (UpwindSelector).