Up to now jQuery has been the only resource required by binder which users had
to load from the internet. To enable binder to work in environments where no
internet access is available this commit adds jQuery 2.1.3 to binders static
files so no internet access is necessary anymore for using binder.
When using Djangos "makemessages" command to collect strings for i18n it only
considers templates with a file extenions of .txt and .html by default. For
more details see:
https://docs.djangoproject.com/en/dev/topics/i18n/translation/#message-files
Also when Django is refering to default template names (e.g. for error handling
or accounts) it always refers to file names with .html as file extension.
To avoid hassle in the future this commit aligns the file extension used for
templates to Djangos default of .html.