Add code-based model validation

[amyheather]

If add queue length can then compare theoretical values with sim values
Theoretical values for m/m/s queue… equations… tell you what should be…

Steady state formula... Littles formula... Get lq... Can work out wq.. TomMonks jackson-network (also on stlite... Qt_lab_mms.ipynb... https://www.overleaf.com/project/66d871e64d4c373b3f2b63cf