Fixed getting max_digits for MySQL decimal fields

Refs #5014.
Fixed #5014 -- Guessed max_digits and decimal_places for SQLite

Decimal is treated as float on SQLite, hence inspectdb can only
guess max_digits and decimal_places arguments.
Imported unittest from django.utils in util_tests

Without this, the 'new' assertion methods are not present with
Python 2.6.
Fixed #16737 -- Support non-ascii column names in inspectdb

Thanks moof at metamoof.net for the report.
Fixed #20169 -- Ensured that the WSGI request's path is correctly based on the `SCRIPT_NAME` environment parameter or the `FORCE_SCRIPT_NAME` setting, regardless of whether or not those have a trailing slash. Thanks to bmispelon for the review.
Relaxed time frame check in test_strip_tags
Fixed deprecation warnings introduced by 97774429aeb54df4c09895c07cd1b09e70201f7d.