If the user has supplied a functional_value, and not supplied a functional_derivative, then apply automatic differentiation to compute the derivative. This is really cool (and was incredibly easy).
If the user has supplied a functional_value, and not supplied a functional_derivative, then apply
automatic differentiation to compute the derivative. This is really cool (and was incredibly easy).

The burgers_mms_diffusion_adjoint test with the functional_derivative removed passes all the tests,
but I can't commit it yet; it depends on the python-uncertainties package, which is not yet installed
by default.

FluidityProject/multifluids,FluidityProject/multifluids,FluidityProject/multifluids,FluidityProject/multifluids