Fixed #17906 - Autoescaping {% cycle %} and {% firstof %} templatetags.

This commit adds "future" version of these two tags with auto-escaping
enabled.
Updated static file example in overview to use static template tag, refs #19675.

Thanks jezdez for the note.
Fixed #19752 - Changed Postgres version numbers to 9.x to avoid having to update them each minor release.
#18899 FileSystemStorage.save should support any file-like objects
Merge pull request #751 from bmispelon/ticket-6271
Fixed regression introduced in 146ed13a.

As override_settings was used after the initialization of the session backend,
we need to use a new session backend here.
Fixed #19811 - Added language code fallback in get_language_info.
Merge pull request #775 from HiddenData/ticket-18899

Fixed #18899 -- FileSystemStorage.save should support any file-like objects
Updated example to use staticfiles static template tag, thanks reinout for the suggestion, refs #19675.
Merge pull request #777 from khalas/ticket_19811

Fixed #19811 - Added language code fallback in get_language_info
Fixed #19827 -- Kept stacktrace in defaulttags exception reraising

Thanks Kronuz for the report and the initial patch.
Minor cleanups in templates test imports
Added test runner option to skip Selenium tests (#19854).
Merge pull request #781 from zsiciarz/ticket_19854

Fixed #19854 -- Added test runner option to skip Selenium tests
Fixed #19609: admin Inlines doesn't display help_text for readonly fields

Refactoring: field was renamed to field_name, since flatten_fieldsets returns field name, not field.

Original patch from Marc Aymerich Gubern
Fixed #15877 -- Improved exception when ModelForm has no model class

Thanks theaspect at gmail.com for the report and volrath for the
patch.
Fixed errors introduced in 21f333bcefccc151d6439246f8203d609ab6ca79. Refs #17751
Fixed errors introduced in 664855b74e1f417384dc7aef35a3df5f86db52d6
Changed %r to %s in get_language_info error message.
Proposed fix for #18162.