Invert nesting of OCS/MHS parts of ics_gen2Actor

ics_gen2Actor is not really an actor: it is launched as a g2cam program, then an actorcore thread is started at a convenient point. Given the relative complexity of the two threading worlds that seemed like the easier choice.

I'd like to invert that, to have it launch as an actor then to start the g2cam threads. Why? INSTRM-345 for one: we would like to have commands like: gen2 realOCS and gen2 simOCS, and to have the g2cam connection be town down and rebuilt. Slightly beyond that, the only calls which MHS needs from Gen2 are the getVisit and getHeader commands; for non-Subaru sites it would be nice to have no Gen2 connection, just simple standalone implementations of those two commands.

How hard is this? I think it'll either just work or be trouble, and it will be obvious immediately.