Consolidate ser/deser in serialize.clj and ddl.clj

[nickmbailey]

We have some mismatch when serializing to/from hector/clojure in the serialize.clj and ddl.clj namespaces. We should rework those namespaces to make sure things match up. The conversion to clojure in serialize.clj is also returning some things still as hector objects (for example comparator type). We should avoid doing that.

This will likely have to be a backwards compatible breaking change so we may need to bump the major version number accordingly.