Improve the error messages for enum deser.
Rejigger dw-metrics.

* Clean up the various classes.
* Flesh out GangliaReporterFactory a bit more.
* Add support for markers to Slf4jReporterFactory.
* Split out dw-metrics-ganglia and dw-metrics-graphite.
* Removed the reporters package.
Fix locale-dependent tests.

Closes #341.