MixedModulestore wraps most getters, update_item, delete_item

Remove tabs.

Refactor student views

Add a second fake translation language

Add Greek language translations

Remove unused imports.

Accessibility improvements to the sequence navigation

Fix pylint/pep8 warnings, use JsonResponse instead of HttpResponse where useful,
put in TODOs to change HTTP status codes to be more accurate.

For a11y, modal dialogs and script templates should be hidden...

Fix pylint violations

Add pycharm helpers to gitignore

Updated title and template for image modal html component

i18n word cloud LMS-2197

LMS-2215

Registration HTTP status code fix for release

Enable (and test) xml export of pure XBlocks

Add the ability to view templates in a browser in development mode

Skip tilde files when importing

fix tests that were breaking on dev envs due to TIME_ZONE='UTC'

Avoid requesting unnecessary thread responses

This adds a simple mechanism to view any template file directly in a browser. The intention is that we can use this to build up reference HTML files which illustrate common UX patterns. We can then view the resulting pages without having to have a working implementation.

In development mode, the URL is /template followed by the path to the template file. For example, you can view the 404 page at:

    /template/404.html

You can also supply string parameters to the template by specifying them as query parameters in the URL.

e.g.  /template/my_template?name=Foo

Remove warning about LTI not working in Preview mode

LMS-2203

Image Modal CMS HTML Block subtype

- Added YAML file for the HTML template code for the modal to work
- Added CSS and JS code for modal to look and function properly
- Updated code to take comments into account.
- Simplified HTML template and expanded JS to set up image modal on load.
- Added preliminary drag script.
- Converted jQuery UI draggable to Draggabilly

screen readers. Also, the mathjax message should be wrapped to prevent
non-IE browsers from complaining about a feature that is IE-only.