tsinghuax i18n changes

Extract strings for i18n
Fix Javascript i18n
Fix Email i18n
Fix JS&Widgets i18n
Corrected LMS main template
Corrected issues with date_utils.py
Revert xmodule i18n: it can't use Django
Reverted i18n changes to section.js
Corrected string formatting
Corrected string formatting issues
Fixed incorrect string formatting
Improved test assertions
Improved tests
whitespace