Cleanup and documentation!
ramp: New class for polynomial ramps. Instantiated in the ForwardModel.
forwardmodel: Now uses new ramp class.
phasemapper: Ramp functionality moved to ramp class.
reconstruction: Ramp order not used, ramp can be now retrieved from the ramp
                class after reconstruction.
analytic, magcreator: Better and consistent definition of pixel centers and
                      their influence on the phase.
testing: Minor corrections for new syntax.

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.

magdata: added convenience functions for flipping and rotating of magnetic
         distributions, fixed bug with ar_dens.
phasemap: now also has a mask which will be used to construct a 3D-mask for the
          magnetic distribution during reconstruction. Added setter/getter.
          Added copy(), scale_down()/scale_up() convenience functions.
          !CAUTION! Only NetCDF4 files save every new parameter!
projector: Fixed hidden bug in X/YTiltProjector, which was problematic during
           tilts over 360°. Now uses linear algebra (much clearer!).
           get_info() function now can be used non-verbose (for filenames).
dataset: added several setter/getter, addes set_3d_mask() for simple 2D tasks,
         renamed mask to confidence (for Se_inv construction)
tests: updated to include the fixes and new functions introduced in this update!

magdata/phasemap: load and save methods now dynamically save with absolute and
        relative paths. Relative paths are defined in the config.py file!