Added a django.template logger without a default handler. Added
logging if there is an exception while resolving variables in a
template.

Added support for multiple m2m fields with the same 'to' model
and with related_name set to '+'.

This introduces a force_append_slash argument for request.get_full_path()
which is used by RedirectFallbackMiddleware and CommonMiddleware when
handling redirects for settings.APPEND_SLASH.

`','`, `'1,,1'`, `',1'` etc. are no longer considered as valid
comma-separated integer lists.

This adds a new method, Apps.lazy_model_operation(), and a helper function,
lazy_related_operation(), which together supersede add_lazy_relation() and
make lazy model operations the responsibility of the App registry. This
system no longer uses the class_prepared signal.

Field.rel is now deprecated. Rel objects have now also remote_field
attribute. This means that self == self.remote_field.remote_field.

In addition, made the Rel objects a bit more like Field objects. Still,
marked ManyToManyFields as null=True.

Previously related fields didn't implement get_lookup, instead
related fields were treated specially. This commit removed some of
the special handling. In particular, related fields return Lookup
instances now, too.

Other notable changes in this commit is removal of support for
annotations in names_to_path().

Thanks Tuttle for the report and draft patch, and Carl Meyer for
help and review.

Consolidated it in one file and move the DOM related stuff to the
template so it is easily overridable. To override the popup behavior
you need to add handlers for the custom events triggered in the
admin_change_form_document_ready template block.

If Field.choices is provided as an iterator, consume it in __init__ instead
of using itertools.tee (which ends up holding everything in memory
anyway). Fixes a bug where deconstruct() was consuming the iterator but
bypassing the call to `tee`.

It's unused since f0f327bb.

Thanks Tim Graham for the review.

When reversing, only outer parameters are used if captured parameters are
nested. Added tests to check the edge cases and documentation for the
behavior with an example to avoid it.

Edited localflavor doc to point to the external package documentation,
leaving just the 'How to migrate' section in Django.