PY-11592 Django 1.6: TEMPLATE_DIRS variable in settings.py is not created properly on project creation

(cherry picked from commit 81c6fb5fc14fee399d156a29da771b021f299470)
Use 'Python' context for 'super' live template (PY-13080)

(cherry picked from commit 73dce39d10a9ce6d08a8df3c430d8701da3aad7d)
Don't suggest Python live templates in comments (PY-13076)

(cherry picked from commit a554bba50da33598579e64194a87b5be7d23c12c)
Don't suggest Python live templates in string literals (PY-12349)

(cherry picked from commit f9685fd38798c2d08089d7d5dad6b105399a8c2d)
Don't suggest Python live templates inside parameter list (PY-12395)

(cherry picked from commit 2322568cdbdf3adda9d2bd548b1a689b07961a52)
Cleanup

(cherry picked from commit 71f507b0dba4de70d6133a9442564f94ca456e2a)
Nullity annotations and explicit TypeEvalContext for PyUnionType.excludeNull()

(cherry picked from commit 846b42a9ed7a613824259afb9b06fa58b386d799)
PY-12981 django apps don't resolve when INSTALLED_APPS is set with '+='

(cherry picked from commit 1b010d04d2e6fb0178f7c5e8b1dcb65854f72e48)
Interpret tuple default parameter value as a weak type (PY-10967)

(cherry picked from commit 06a130f93dd1e68903e83580f2429dee199cbc66)
Use union of types of members as iteration type for tuples

(cherry picked from commit a1d93e0756574c4e5913ffdfc34d1d4443c06b69)