Fix extras_require and environment markers in sdist

Currently, environment markers in extras_require (e.g. {':python_version=="2.6"': ['unittest2']}) in sdist do not work.
The plan is to use pkg_resources.Distribution which will give it for free.

First commit is to make sure we do not put editable_options in extras (parse_editable return types are currently merging the two).
Well it was there for sdist so I've added it for wheel also.
But I'm ok to switch it to debug or remove it completely since the extras is likely to have been already logged through the req_install before.