Redone interning capabilities.
Introduce intern-owl function.
All def* macros now use intern-owl function.
Added intern hook.
Reworked intern-entity in read.clj to use intern-owl.
This now means that all the interning is done in one place, which
is cleaner.
Lookup now longer needs explicit caching, as it uses the intern hook.
render, and repl updated to reflect this.
Fixed small documentation error.
More documentation.