Updates for the adjoint optimisation library

A number of updates related to the adjoint optimisation library.

The branch contains mainly enhancements in the infrastructure of the objective functions, the computation of sensitivity derivatives for shape optimisation and some minor new features like the adjoint to the rotatinWallVelocity boundary condition and the introduction of a new objective function minimising the square of the turbulent viscosity over a certain volume, which can be used to qualitatively approximate (and then minimise) noise (see also the header of the corresponding class for a bibliographic reference).