ECOM-3638

 The CCXCon app is used to push course updated to the CCXCon
 externale service.

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

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.)

remove references to middleware that were missed previously

use key apis rather than local implementation of key conversion.  remove local implementationa

remove spurious test for attribute

fix test setUp to avoid unneeded flattening

code quality fixes

add security check ensuring that the coach is coach for *this* CCX.

prevent ccx/deprecated course id problems

1.  do not allow ccx objects to be created if the course id is deprecated
2.  filter out any ccx memberships that involve deprecated course ids (in case there are bad ccxs in the database)

Fix test failures and errors arising from incorrect code path execution

Create context manager to handle unwrapping and restoring ccx values for the modulestore wrapper, employ it throughout modulestore wrapper implementation

This makes these files importable, and puts them into the new best guess
as to where files should live.

This reads configuration directly from yaml
and imports it directly into settings