Improvement: ox.lang.* rather than editing in place

[arrdem]

As the whole-lang branch stands, I'm just trying to hack clojure in place. This means I'm restricted to the set of language changes I can make without impacting the tooling upon which Oxcart itself is built. Since self-hosting is not a goal, the obvious fix is to just return to depending on clojure 1.6, and to move what is currently the clojure core source to ox.lang both in java and "clojure", and create special casing code so that some mapping exists between clojure.core namespaces and oxlang namespaces allowing the loading engine to compile the appropriate code.