Change TPCH dates to be DATE type

Fix date handling bugs in query tests, kafka tests, and jdbc connector
Map DATE to TEXT in Cassandra connector
Don't cache instantiated parametric types
Fix equals() and hashCode() on TypeSignature
Fix lookup of parametric types

Looking up a parametric type would fail if the name given was upper
case. Make the lookup case insensitive to match other type lookups.
Add release notes for 0.87