Neighbourhood definitions

[HeleNoir]

The item in #90 "allow for local best and global best orientation" requires thinking about and implementing different neighbourhood definitions. I think these should be general, rather than PSO specific.

Specifically, there are several ways to define the neighbourhood and several topologies for some of those definitions. For each, however, it is required to

• specify the number of neighbours to compare to

The different ways to compute the neighbourhood are either based on some distance measure in the search space, or, in case of some PSO implementations, on the positions of the solutions in the array, with some corresponding topology. Thus, we require:

• a neighbourhood definition based on the euclidean distances between the solutions
• a neighbourhood definition based on the positions in the array with a
• ring topology
• square/von Neumann topology
• wheel topology

and star topology, but this is the global best we already have.