Create Network class

One of main classes in our simulator.
It is supposed to have features like

### Setup
This part will call the Column class.
Create several areas consist of columns and connect them with experimental data.

### Save into file
Save the whole network structure into a file with a hash label, so that it can be built faster when reuse it.

### Read and build from file
Initialise a network instance from params, but also a network file with hash label.