More random selection of crew

[fingerboxes]

Crew selection is too deterministic for my taste still.

Rough Idea:
*Pass entire Vessel, ShipConstruct, or VesselCrewManifest\IEnumerable of PartCrewManifest.
*Parse this to obtain groupings of open slots and requirements thereof.
*This should be the same order as VAB/Launch Window.
*The first element will be assumed to want veterans, subsequent elements will be assumed to want newbies

*Group AvailableCrew by Rank, then by Job Title.
*Select a random crew for each slot from relevant rank.