Allow non-String user values in work-unit data

[jdanbrown]

A small generalization to allow clients to stuff their own metadata into work-unit znodes: Json.parse[Map[String, String]](workUnitData) -> Json.parse[Map[String, Any]](workUnitData).

[jdanbrown]

I agree that this change gives users more opportunity to use zk as a database instead of a coordination system, and I think that they shouldn't do that. ;)

[eribeiro]

So even more a reason to not even open up this possibility! If you leave your backdoor open in the hopes nobody will break in, then, believe me, they will eventually break in.:-)

Again:

UPDATE: Have you evaluated the effect of those ClassCastException failures on Ordasity through tests? It would be cool to commit a unit test to do so. The comparison of 'junk' with node id bears false while throwing a runtime exception may potentially have unpredictable results, doesn't it? See, I am assuming I can be totally wrong. :)

UPDATE 2: Just out of curiosity, what kind of confusing behaviors?