Also added tests for HStoreField and JSONField.
Thanks Aleksey Bukin for the report and Tim Graham for the initial patch and
the review.
Backport of 928c12eb1 from master.
Note this means the serialization of e.g. IntegerRangeField now has
strings for lower and upper, so use to_python when they came back in
(same behaviour as ArrayField, hopefully, from where I also got the
set_attributes_from_name function).
Provide `contained_by` lookups for the equivalent single valued fields
related to the range field types. This acts as the opposite direction to
rangefield__contains.
With thanks to schinckel for the idea and initial tests.
Added support for PostgreSQL range types to contrib.postgres.
- 5 new model fields
- 4 new form fields
- New validators
- Uses psycopg2's range type implementation in python
