Integrate pyros_setup

[asmodehn]

Probably just a part of it...

The goal is not to setup a distro exactly like ros does, but only to discover the different distros available and set them up (with something like site.addsitedir()) so that python can import from that and use them.
that might be enough to work with ROS systems, from python land...

[asmodehn]

It seems the intentions for the import mechanics is to have the MetaPathFinder playing the role of the ROS distro...
This should be investigted in details, and hopefully we could integrate most of pyros_setup into the metapathfinder and this way get a proper pythonic interface to ROS environment...