Flesh out Clojure support

[pokey]

#375 adds preliminary support for Clojure, along with lots of tests, but it needs to be tried by a real Clojure user to see if it feels right, and it is missing a few aspects:

• Handle formal function parameters for argumentOrParameter
• Handle let declarations, defs, etc by support name / value parity pairs like we do for key / value in map literals
• Have "value" select the body of a function, branches of "if statement", etc