This commit adds defaults for the options
`--destination-collection`, `--destination-service-url`,
and `--destination-token`. By default they are set to
the parameters `COLLECTION`, `SERVICE_URL`, and `--token`.
This makes it easier to specify a different collection,
or service URL, because only options for the elements that
change for a new collection or service URL have to be provided.
For example, auto-curating to a different collection in the
same service with an identical token only requires to specify
the option `--destination-collection` (in addition to the required
arguments).
