Moved basis function from outer if statements to function argument

The purpose is to merge 1D, 2D, 3D functions into one
Added the possibility of calculating the dist table in 3D through
Monte Carlo integration.

The Monte Carlo method seems to be competitive in 3D, especially for
fast testing purposes.

It is possible to perform a fast and dirty approximation with 1e3-1e4
points or generate more points, to generate better approximation with
more time.
added missing dependency
Reduced the number of PEP8 flaws, moved dist_table points probing to potentials module
Updated docstrings

Changed docstring convention to similar to Numpy,

Also:

* moved distance_table indices juggling from KCSD1D, KCSD2D, KCSD3D
  into dist_table_utils.generated_potential
* added test case testing for zero pot/csd output in KCSD3D
improving PEP8 compliance

* reduced the number of PEP8-related flaws
* added 1D source distribution tests