Refactoring: Replaced MagData with VectorData and added ScalarData class (and common superclass FieldData).
magnitude is now called field (which is more appropriate)
projector now uses FieldData to process both vector and scalar data (foundation was in place before)

Phase maps now also have a mask and a confidence matrix.
Began new script structure (temporary folders created).
Cleanup, logging and documentation done.
config: NTHREADS is now set here.
dataset: Method for creating 3D masks added.
phasemap: Mask and confidence matrix added. Padding and cropping supported.
forwardmodel: Stubs for multiprocessing added (next TODO!).
kernel: Added support for perturbed reference wave.
magdata: Padding and cropping supported.
projector: New property 'sparsity' introduced.
regularisator: Stub for ComboRegularisator added (next TODO!).
tests: Changed accordingly.