Please note that this is a squshed commit and the work of:
Symbolist, macdiesel, nedbat, doctoryes, muzaffaryousaf and muhammad-ammar

Includes info about the serversonly/testsonly pattern, as well
as multiprocessing.

TNL-3137

TNL-3137

https://github.com/edx/edx-platform/pull/9345

TNL-3137

The old line:

    from path import path

produced pylint errors because of the baroque way that path.py defined
"path".  We tried to get them to change how they defined it, but they
deleted the name instead: https://github.com/jaraco/path.py/issues/102

(Jason then changed his mind, but this is a better way to use path.py,
it avoids the pylint error at least.)

Adding information about paver

JShint will be executed with paver run_jshint, which will use a defined set of
directories (likewise defined are directories to ignore). A limit can be imposed
on the total number of violations. Note that this change does NOT include adding
jshint to diff-quality or `paver run_quality`.

Fix typo

And cleaned up one doctoring

This allows developers to pass the `--pdb` flag to paver test commands,
and that flag will be proxied to the `nosetests` command. It's useful
for debugging purposes.