add a backend argument?

[petrelharp]

I think that we'll want to be able to specify which backend to use, once we have the ability to use a SLiM backend.

[grahamgower]

There will also need to be a way to specify backend specific parameters. It will get a little messy if they're all thrown in cli.py: top_parser. I propose that there be a Backend class, with an add_backend() method, so that various backend specific things can be specified (like currently exists for species or models). At a minimum, a backend would have a name, an empty list of CLI args, and implement a simulate function that follows the msprime.simulate API.

[jeromekelleher]

I agree we'll need a generic interface for the simulation engines (is "backend" a big vague?). Your ideas here seem very logical to me.

[grahamgower]

SimulationEngine is fine too.

[andrewkern]

closing this down as I believe #187 resolves this issue. feel free to reopen if necessary