Ensemble Enhancements

[Robadob]

These were left over from the PR, but none-blocking

• Import/export RunPlanVec to file ability.
• There was originally a plan to have code that estimates max concurrent models by estimating memory usage.
• If CUDASimulation errors out during ensemble, currently no information is captured (I think it's just printed to (stderr or stdout). Might want a nice way of logging these errors.

[Robadob]

Was thinking about CUDAEnsemble error reporting or lack thereof, may have thought of a suitable approach: New CUDAEnsemble::EnsembleConfig parameter error_level or fail_mode.

• 0 or None: Runs which fail do not cause an exception to be raised. Failed runs must be probed manually via checking the return value of calls to CUDAEnsemble::simulate(). If quiet is set to true, runs will not be printed to stderr. (This is the current behaviour, however CUDAEnsemble::simulate() currently returns void.)
• 1 or Slow: If any runs fail, an EnsembleException will be raised after all runs have been attempted, before CUDAEnsemble::simulate() returns.
• 2 or Fast: An EnsembleException will be raised as soon as a failed run is detected, cancelling remaining runs.

Would need a decision on the most appropriate default error level, probably 1 imo.