Fix psycopg2 bulkloader docs

[fromm1990]

The cursor.copy_from function in newer versions of psycopg2 does not support the schema.table format but escapes it with "schema.table" (should be "schema"."table" instead). Therefore, the documented bulkloader breaks when the schema is explicetly defined in the name of a PygramETL table definition (Dimension or Fact).