enabling restart option with cosmomc format output files

[am610]

I noticed the restart chain option is not available when output file format is set to cosmomc. I would like to please ask if this can be made possible.

thanks

[joezuntz]

I would really strongly recommend moving away from the CosmoMC format. It loses almost all metadata and provenance information about a chain. I'm not saying the cosmosis format is perfect and I'd love to hear ideas about improving it, but it really is better than the cosmomc version.

I probably can't devote the time to this particular feature but would be happy to look at a pull request.