* make `user_status` more intelligent
* remove some logic from the templates
* rename `parse_error_msg` to `parsed_error_msg`
* fix up and add more tests

LMS-1387

LMS-1387

Studio: revises CSS reference/pipeline architecture for better organization, reduced redundancy, and to handle IE9 selector limits

Bug: LMS-1363

The error was caused by the CONFIG_ROOT environmental variable,
which was incorrectly assumed to be a path.py valid path.

Was re-introduced in a bad merge.

This reverts commit a517dc20.

add middleware to detect students with disabled accounts

add tests

This reverts commit ec01253e, reversing
changes made to ae8c9710.

change to use regex to do the domain mappings. Also add config to AWS to be able to set from configuration file.

handle cases where HTTP_HOST is none, like in unit tests

add linefeed at end

fix up regex matches

switch to use thread local storage to hold the request itself

.

.

convert over to use open source 3rd party library

convert over to use django-cum

add unit test

remove comment

.

add comment to config setting

fix comment

use better regex for localdev

no need to break

no need to wrap an imported function, it's visible to any file that is importing us

add comment

add unit test

clean up test

use a separate env file to set the preview hostname

@jzoldak showed me that setting `USE_I18N = DEBUG` didn't actually accomplish
what I had hoped it would -- changing DEBUG didn't also change USE_I18N.
This pull request accomplishes what I was trying to accomplish, without being
quite so clever about it.

as a first step to separating db connection from modeling
and to support location mapper and contentstore using same db config as modulestore

The env variable CONFIG_ROOT is used to determine the location of the
JSON configuration files. This is useful when a deployment of the
platform is used to access different environments when executing django
commands.

We want USE_I18N to be on in development, but off in production. Tying
this setting to the DEBUG setting accomplishes that neatly.

use to instantiate loc_mapper
test loc_mapper injection into split modulestore

   And include Don's fix for partial course_id lookup.

cleanup

Updates.

Testing changes.

Testing changes.

asset-index progress state cleanjup.

cleanup

* Add unit test coverage for this "exclusion from tracking" logic
* Exclude based on regex match instead of raw string comparison
* Exclude heartbeat requests from tracking