Openbazaar python launcher

new pull request after 1st round of reviews.
Thanks @Renelvon this has the merged changes from your repo.

(@Renelvon I kept that REVERT commit you put there as I'm not sure I understood what was right or wrong about it, I figured it'd be easier to fix here now)
Please don't. Leave them as is. Once this is merged, I will try to refactor the parser so that a nicely styled `usage` message is automatically built.