Update coordination handling in "generate" module

[aramyxt]

More accuracy could possible be achieved by weighing values based on histogram curves of coordination numbers.

Right now, generate_network() relies on pulling and editing the generated network based on random sampling of a large sample size (of coordination numbers).

[aramyxt]

Since most of the coordination numbers tend to hover around the mid range of the actual coordination numbers, we can try to redistribute pore throats using OpenPNM topotools to help with the range imbalance. We could also remove the 8 max pore coordination limit.