Enable Java interop in any namespace

Fixed an issue where interop functions would become unavailable if the user switches namespaces. Adds a dependency for rewrite-clj (and ~100KB to the unzipped package) which I'm not sure was a good idea because I probably could have just used a regex. It also duplicates functionality of the Lezer parser, which I probably also could have used.

Also fixed a bug that the editor contents could be evaluated while there was still an uncleared result. Now we simply run clearEval() prior to each eval.