This is a quick-and-dirty converter built to export the contents of a PostgreSQL
database to a JSON file for later import to MongoDB.

Some details:
- I was combining two Trac databases into one, so I needed to
-- record which database each row came from and (_connectionURL)
-- only drop a target collection once (dropped)
- PostgreSQL appears to put all application tables in the "public"
  schema with type "TABLE"; these values are both hard-coded.
- NOTE IN PARTICULAR that this does not export "SEQUENCE" objects,
  which may mean that information important to your application is lost.
- This should work with any JDBC source, give or take those two
  hard-coded values.
- The ultimate target was MongoDB, so:
-- the output rows are templated as MongoDB commands
-- any table named "version" is skipped