wip: removing format/context from constructors
fix: added findZCTcoords signature

added a signature that accepts a DatasetMetadata so proper
effectivesizec calculations can be made.
WIP: restructured format and translator discovery

Translators are now discovered independently via a TranslatorService.
There is no longer a mapping between formats and translators, because
the relationship is many to many (e.g. if someone created an APNGtoICS
translator it would have no defined format).
fix: extracted PluginAttributeService interface

removed pluginClassService