Fixed #20204 - Consistent usage of url() in URL dispatcher documentation

Thanks Baptiste Mispelon for the patch and dave.lampton@ for the suggestion.
Fixed #20237 -- Reenabled assertContains with binary parameter

Thanks Baptiste Mispelon for the review.
Changed a deprecated warn() call in libgeos
remove confusing phrase from DecimalField docs

The phrase "if it exists" was used in reference to the `decimal_places`
argument to `DecimalField`, when in fact that field is required.
Merge pull request #1008 from reverie/patch-2

Removed incorrect phrase from DecimalField docs.
Fixed #20243 - Clarified when RelatedManager.remove() exists.
Documented BoundField.label_tag
Fixed #20211: Document backwards-incompatible change in BoundField.label_tag

Also cleaned up label escaping and consolidated the test suite regarding
label_tag.
Fixed #20248 - Clarified manage.py vs. django-admin.py
Fixed #20237 (again) Allowed binary parameter to assertContains
Fixed #20252 -- Mentionned geojson Spatialite support from 1.5

Thanks burton449geo at gmail.com for the report.
Modified forms_tests to work with unittest2 discovery.
Modified test_utils to work with unittest2 discovery.
Modified test_client_override to work with unittest2 discovery.
Modified comment_tests for unittest2 discovery.
Modified generic_views for unittest2 discovery.
Modified model_fields for unittest2 discovery.
Modified template_tests for unittest2 discovery.
Modified utils_tests for unittest2 discovery.
Modified validation to work with unittest2 discovery.