This commit adds the `dtc` subcommand `import`.
`import` reads records that were written by `export`
from a file system and inserts them into a
dump-things-server. This includes the curated
area and the incoming areas.
By default the destination server URL and
collection name is read from the file
`description.json` in the exported data area.
Both can be overriden by command line options.
The file `description.json` is part of
an export and contains information about the
exported data.
This commit adds the two fiels:
- date: the date of the export
- service: the URL of the dump-things-server
from which the data was exported
The commit also removes a "chatty" message
about empty incoming areas.
