Implement exceptions in HDFWriterModule.h

Created by: mchorazak

Throw exception in HDFWriterModuleRegistry::find(std::string const &key) if key not found.

https://github.com/ess-dmsc/kafka-to-nexus/blob/9cf7b41ebeacec0b2ac1dbb55aecce9b4c307797/src/HDFWriterModule.h#L223-L224