Add `--minutes-wait` option to CLI

Similar to `--wait` for `bin/omero chgrp` and friends,
setting `--minutes-wait` for the import process disconnects
once the files have been transfered. "Disconnectin from..."
is printed to the CLI and the process exits. Currently, the
`ImportProcessPrx` is left open on the server and must be
manually closed.
Improve name of servants

Import processes returned from:

```
  bin/omero shell --login
  client.getStatefulServices()
```

previously had very opaque (UUID-based) names.
This commit adds a readable string to them.
Add `--close_completed` advanced option to the CLI

To re-claim resources left open with `--minutes_wait`,
the new `--close_completed` option checks for any process
**in the current session** and closes it.

```
$ bin/omero import -- --minutes_wait=0 ...
... Disconnecting from import process...

$ bin/omero import -- --close_completed
Done: f318cbda-d91d-4123-bef4-467e5c4393e4/e7c27250-ac59-4337-bb0f-efd6fdb47fbd-ManagedImportProcessI
1 service(s) processed
```

For closing in other sessions, it will be necessary to first
find the sessions and join them.