WIP, but main extractor paths seem to work

This adds a possible macro for building JDBC type sources.

Right now just a size annotation, also might need an unsigned one.

Number of types available probably needs to increase. But it seems to build most of the info we would need for a source
the default value might not fit an Int, right? Or did you mean 32 bit int here? Maybe better to have Long as the type if we are dealing with a superset.