Test overflier-climber scenarios in BlueSky

[thobson88]

Steps:

• generate a sector
• generate an overflier-climber scenario
• run the scenario in BlueSky with the "default policy" agent, i.e. the agent that follows the rule: "climb as early as possible" (*)
• step through the simulation
• record the two aircraft lat-long positions at the crossover flight level, i.e. the overflier's flight level, in some output data table (that should also contain the parameters used to generate the sector & scenario); from this we can check whether (and where) a loss of separation occurred (it should happen near the centre of the sector);
• repeat with different sector shapes & sizes, different aircraft types and different initial flight levels

(*) Since this requires the "default policy" agent, it depends on the in-progress OpenAI Gym integration in Dodo.