Suppress unwanted warnings in GeoModelIO

This MR adds proper logging to GeoModelDBManager and suppress unwanted warning messages from being printed to std::cout independently of the log level.

In particular, it suppresses the warnings about missing tables for new GeoModel nodes/classes in older .db files: we want to be free to develop and add new classes without invalidating the earlier DBs.

The MR also removes old and unused code.

This MR closes #115 (closed)