wrap long words in field labels on admin forms, closes #18755

Otherwise, words overlap into the fields themselves, which makes the labels
unreadable.
Fixed #16123 -- Ensured strptime receive proper string type

strptime generates an UnicodeEncodeError when using a non-ascii
unicode string on Python 2.
Fixed two malformed links.
Fixed #19677 -- Introspection of recursive foreign keys under SQLite.

Thanks Simon Charette.
Fixed #19676 -- Supported 'self' foreign keys in inspectdb.

Thanks Georgy Kutsurua for the report and Simon Charette for the patch.
Added HTML5 email input type

Refs #16630.
Added HTML5 url input type

Refs #16630.
Fixed #19683 - Added a missing import in signing example.

Thanks sunsongxp@ for the report.
Updated metrics on the documentation.
Fixed #19690 - Removed unused import
Removed an import of a class unused in the Ajax example.
Fixed typos in docs and comments
Implemented some SpatiaLiteOperations as cached properties

Previously, some properties weren't set unless
confirm_spatial_components_versions() was explicitely called.
Fixed #19552 -- Enhanced makemessages handling of ``{# #}``-style template comments.

They are simply ignored now. This allows for a more correct behavior when
they are placed before translatable constructs on the same line.

Previously, the latter were wrongly ignored because the former were
preserved when converting template code to the internal Python-syntax
form later fed to xgettext but Python has no ``/* ... */``-style
comments.

Also, special comments directed to translators are now only taken in
account when they are located at the end of a line. e.g.::

  {# Translators: ignored #}{% trans "Literal A" %}{# Translators: valid, associated with "Literal B" below #}
  {% trans "Literal B" %}

Behavior of ``{% comment %}...{% endcomment %}``tags remains unchanged.

Thanks juneih at redpill-linpro dot com for the report and Claude for
his work on the issue.
fixed minor typo #19703
Fixed #19160 -- Made lazy plural translations usable.

Many thanks to Alexey Boriskin, Claude Paroz and Julien Phalip.
Fixed #19076 -- Added content_type attribute to TemplateView.

Thanks Gavin Wahl.
Changed "versionadded" after the decision to backport.

Refs #19076.
Fixed #19034 -- Added proper i18n pluralization for max/min length validation messages

This was made possible by commit 3f1a0c0040b9. Thanks Evil Clay
for the report and Alexey Boriskin his work on the ticket.
Added file forgotten in 23e319d7.
Merge pull request #686 from skrr/ticket_19703

Fixed #19703 -- Typo in get_declared_fields docstring