Fix bug 849913: Fix unicode issues with video titles and descriptions.

Vimeo can't accept encoded UTF-8 in API requests, but it can accept
HTML-entity-encoded text, so we encode titles and descriptions as ASCII
and convert any unicode characters to HTML/XML entities.

Other fixes:
- Remove django-csp from the app list as the migrations for csp break my
  local MySQL database and we aren't using reporting anyway.
- Add /video/upload/error/ URL that accidentally got removed; the upload
  error code in the JS uses it.