Still to do: PhaseMapperElectric does not work
             3D reconstruction does not converge

minor changes to plotting methods (PhaseMap now plottable without colorbar).
phase_map: gain can now be set to 'auto' (5 fringes, determined by max. phase).
renamed 'density' to 'gain' (makes more sense).
regularisator: started to include norms and more kinds of regularisations.
mag_slicer: GUI which can go through loaded magnetizations along the major axes.
paper 1: minor changes to the scripts for the results.

regularisator: new module to represent different regularisation strategies
costfunction: changed to use the new Regularisator classes, changed arguments!
dataset: fixed bug that always displayed the own phase maps instead of provided
reconstruction: changed to use the new Regularisator classes, changed arguments!
scripts/rueffner_file: tried to avoid Memory Error (no success)
scripts/zi_an: added holographic contour plots with overlayd magnetization
scripts/reconstruction_sparse_cg_test: now uses Regularisator classes and plots
                                       phase differences (original - reconstr.)

projector: ALL projectors can now handle arbitrary dimensions
dataset: reverted to old strategy (dimensions must match)
reconstruction: least square method now also with regularization of order 1
scripts: cleanup and streamlining, added projector_test

dataset: phase map dimensions do not have to match anylonger
        (just with the connected projector)
reconstruction: simple least square: added regularisation of 1. order
scripts: stuff which will be cleaned up in next commit

pep8: optimizations
phasemapper_core: numcore module for phasemapper
scripts: compatibility with new structure
reconstruction: new scripts

Renames:
datacollection --> dataset
optimizer      --> reconstruction

scripts:
interactive_setup is now implemented in an extended Spyder startup file.
some other scripts are now
the rest is NOT adapted, yet, which is the next task at hand
furthermore scripts will be sorted and unused ones deleted in the next commit