Tie the USE_I18N setting to DEBUG setting

We want USE_I18N to be on in development, but off in production. Tying
this setting to the DEBUG setting accomplishes that neatly.
Add variable to set location of config files on aws

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.
Segregate the mongo db config from the modulestore config
as a first step to separating db connection from modeling
and to support location mapper and contentstore using same db config as modulestore
Change the default FROM address for bulk email
Replace Language with Event Source in the tracking logs documentation

Also:
  - Add some missing event descriptions
  - Reorganized rows to put relevant events together
Merge pull request #1246 from rocha/add-event-source-in-data-docs

Add event source in data docs
Studio: changes drag and drop container to new .wrapper-dnd on outline/subsection views
Wait between clicks for new component
Guard against StaleElementException in css_click
add acceptance tests for event tracking
Merge pull request #1235 from edx/db/tie-i18n-to-debug

Tie the USE_I18N setting to DEBUG setting
Clarify USE_I18N settings

@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.
Add retry logic if element not found
Use a better metadata_cache_key

The old code created keys like "('course', 'org')", and the space
character caused a warning from Django during tests.  Also, strings are
probably better than tuples for keys.
Merge pull request #1266 from edx/talbs/studio-dnd

Studio: Drag and Drop Container
Put XBlock css and javascript onto the LMS courseware page

This required changing structural XModules to fully implement
student_view, rather than just returning the HTML of their children in a
get_html call.

[LMS-223]
[LMS-1170]
Remove the now-unused import.
Merge pull request #1207 from mulby/gabe/tracking-tests

add acceptance tests for event tracking
Merge pull request #1221 from cpennington/lms-xblock-css-js

Put XBlock css and javascript onto the LMS courseware page
make drag_and_drop component work with requirejs and changed static url