Better detection of stdlibs in virtualenvs

There are two possible system paths if hacking is
running in a virtual environment; the virtual
environment and the system packages. `os` is often
copied to the virtual environment, `logging` is
not. This adds the logic to detect them both as
stdlibs for import linting.

Change-Id: If6e168879517ecbffbede6bf7e641f6eed757da4
Detect egg-linked libraries as third-party

By default, when pip install downloads a library
that is referenced with the `-e [url]` format, it
gos in a ./src/ directory. imp.find_module does
not find those, so we pick them up with a path
check.

Change-Id: I70d25e769773dc75b153cd92259424506a87eaf0