use djangos method of wiping sqlite3 tables

Django uses a reference graph to determine the order
in table deletions that occur. Do the same here.

This commit also adds in the `REGEXP` sqlite function,
exactly how Django uses it in its reference graphing.

Signed-off-by: Kevin Morris <kevr@0cost.org>

test/test_db.py

@@ -200,6 +200,9 @@ def test_connection_execute_paramstyle_format():
             aurweb.db.kill_engine()
             aurweb.initdb.run(Args())
 
+            # Test SQLite route of clearing tables.
+            setup_test_db("Users", "Bans")
+
             conn = db.Connection()
 
             # First, test ? to %s format replacement.