Combined this and the checker of
SUPERTYPE_INITIALIZED_WITHOUT_PRIMARY_CONSTRUCTOR together.
Also fixed SUPERTYPE_INITIALIZED_WITHOUT_PRIMARY_CONSTRUCTOR incorrectly
repoted as warning instead of error.
- Add utilities to add new attribute to ConeAttributes
- Get rid of FlexibleNullability attribute (it can be easily inferred
for any flexible type at any moment)
- Fix determining of EnhancedNullability attribute