Fully working 1D implementation and tested with analytics.

Included features:

• geometries: 1D mono_layer, bilayer
• operators for the 1D:
  • all sparse matrices, like the divergence, gradient, laplacian, poisson, are computed using python functions
  • dense matrix calculation included for mono- and multilayers using python
  • interlayer exchange for 1D only!
• relaxation
• eigensolver:
  • on can specify a wave vector array using disp = exp.eigenmodes(...,k=k_array,...)
• dipolar operator: based on the dimension the solver for the first potential is selected between the direct spsolve(...) and the iterative ```bicg(...)`` biconjugate-gradient solver
• in sample.py the computation of operators will be called based on the dimension