Add filesize upload limit for GridFS.

Change file size when committing final changes

Implement js guard against large file uploads.

TODO @stvstnfrd to review changes

Fix status code and styling issues for
server-side handling of large file uploads.

Add UPLOAD_CHUNK_SIZE_IN_MB settings constant for
the front-end, and improve commenting for these
constants.

Revert whitespace changes

Standardize variable names across front/backend.

- Note: also fix an i18n issue with format string
for upload modal

Move Notification from main.coffee to assets.js.

Reverted main.coffee

Remove unused constant

Move clean_large_asset to tearDown function

Add override for asset limit constants for tests.

Improve var style; remove extra gettext() call

- Renamed faq url variable across files based on
feedback from @stvstnfrd

Improve js and python variable names

Add i18n for upload file size error message

Remove unused argument variable "d"

Indent arguments and add trailing comma

Mock file size and add sm/md/lg file upload tests.

Remove const overrides since we mock file uploads.

Fix syntax / async issues with file upload modal.

Fixed js syntax issue with early semi-colon.
Fix i18n issue with js multi-line strings.
Fix interleaved callbacks; startUpload could be called before fileupload
callback, so set a constant for startUpload to check.
Fix UI show/hide issues so that the embeddable elements are hidden on
file upload.

Final round of changes to GridFS issue.

Add @ddt to UploadTestCase.
Update external url in common.py to point to working page.
Fix js / python var naming.