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- previously introduced `getOrDefault` as a dictionary _get_ method,
  now complete the transition and use it everywhere instead of
  `lookupOrDefault`. This avoids mixed usage of the two methods that
  are identical in behaviour, makes for shorter names, and promotes
  the distinction between "lookup" access (ie, return a token stream,
  locate and return an entry) and "get" access (ie, the above with
  conversion to concrete types such as scalar, label etc).

When more than one volumetric B-Splines control boxes are present, the
sensitivity constituents corresponding to the non-active design
variables were not bounded(zeroed) correctly. The resultant
sensitivities, used in the optimization, were bounded correctly, so this
was more a bug pertaining to the output file of the sensitivities rather
than a functional one.

- The core of the FatalIOError message was not printed due to exiting
  with FatalError instead of FatalIOError
- Changed the TypeName in all derived classes of displacementMethod so
  that the toc printed by the FatalIOError corresponds to what the user
  should add in dynamicMeshDict

- Failed due to double*Matrix<float> multiplication.

Style changes

- use SquareMatrix with Identity on construction

- use Zero in constructors

- remove trailing space and semi-colons

The adjoint library is enhanced with new functionality enabling
automated shape optimisation loops.  A parameterisation scheme based on
volumetric B-Splines is introduced, the control points of which act as
the design variables in the optimisation loop [1, 2].  The control
points of the volumetric B-Splines boxes can be defined in either
Cartesian or cylindrical coordinates.

The entire loop (solution of the flow and adjoint equations, computation
of sensitivity derivatives, update of the design variables and mesh) is
run within adjointOptimisationFoam. A number of methods to update the
design variables are implemented, including popular Quasi-Newton methods
like BFGS and methods capable of handling constraints like loop using
the SQP or constraint projection.

The software was developed by PCOpt/NTUA and FOSS GP, with contributions from

Dr. Evangelos Papoutsis-Kiachagias,
Konstantinos Gkaragounis,
Professor Kyriakos Giannakoglou,
Andy Heather

[1] E.M. Papoutsis-Kiachagias, N. Magoulas, J. Mueller, C. Othmer,
K.C.  Giannakoglou: 'Noise Reduction in Car Aerodynamics using a
Surrogate Objective Function and the Continuous  Adjoint Method with
Wall Functions', Computers & Fluids, 122:223-232, 2015

[2] E. M. Papoutsis-Kiachagias, V. G. Asouti, K. C. Giannakoglou,
K.  Gkagkas, S. Shimokawa, E. Itakura: ‘Multi-point aerodynamic shape
optimization of cars based on continuous adjoint’, Structural and
Multidisciplinary Optimization, 59(2):675–694, 2019