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)
not sure where is the code repetition, gotta iterate to generate the right database paths and create a context per OpenBazaar instance.

If you put it in a factory method you'd still be doing the same thing, please expand, I guess I'm not following.