Allow Cyclus runs from within Cypher

[dean-krueger]

The initial edge of Cypher was set conservatively to being able to generate Cyclus input files, but not to run them. It was always planned to allow Cyclus runs from within Cypher, similar to how you can run OpenMC. This PR adds the necessary code to allow:

sim = cypher.Simulation(control)

# Add RIF, recipes, etc

result = sim.run()

such that it should then be possible to do:

db = cymetric.dbopen(result.output_dir)
...

and hand the output of the simulation off to cymetric directly within the same notebook. This hopefully creates a seamless workspace experience for users, who should be able to only ever interact with Cyclus through an ipython notebook if they want.