* implementation work for json importers
* json driver checkpoint
* working on json.ParseObjectsInArray
* json.ParseObjectsInArray seems to be working
* checkpoint while tidying up ParseObjectsInArray
* more tidy checkpoint
* more tidy checkpoint 2
* tidying up ParseObjectsInArray
* tidy up
* code/docs cleanup
* more cleanup of json driver
* more cleanup of json driver
* flat json import seemingly working
* improvements to json driver
* json writer now prints empty [] for postgres empty tables
* improvements to sqlite source metadata query
* table metadatawriter colorization tuning; minor testh.Helper refactoring
* cleanup of metadata for multiple drivers
* more cleanup of source/table metadata
* yet more cleanup of source/table metadata
* improvements to mysql SourceMetadata
* improvements to mysql TableMetadata
* yet more fiddling with mysql metadata
