Logging registration of JAI ImagingListener [GEOT-4797]

ImagingListener used as a bridge from JAI error messages to GeoTools logging system.

See https://jira.codehaus.org/browse/GEOT-4797 for discussion.
Fix up javadocs around GeoTools init method
Merge pull request #453 from jodygarnett/jai_msg_filter

Log JAI messages [GEOT-4797]