Deprecate NumEqVector property

Replace by Dumux::NumEqVector type trait in dumux/common/numeqvector.hh

changed milestone to %3.4

added Cleanup label

created merge request !2567 (merged) to address this issue

mentioned in merge request !2567 (merged)

mentioned in issue #1009 (closed)

closed with merge request !2567 (merged)

mentioned in commit f735d278