Control panel should show numbers in each population #749

It's quite difficult to determine the number of cells in a generated network, and especially if you set a cell density you're never sure of the total number in an instance of the network. A good place for this would be the Control Panel, where you can list the instances if you expand the individual cell populations. What would be better is if the number in each population was visible beside the name, and mayne the total at network e.g.

> network (30)
  > E2 (6)
  > L1 (3)
...