Add batching to attachCompanionFilesToImage (See #12485)

As with other methods in `OMEROMetadataStoreClient` which have run into `Ice.MemoryLimitException` issues, the `attachCompanionFilesToImage` needs batching to not attempt saving too many objects at one time. This is mostly a workaround; in fact, we should no longer be generating companion annotations since that information is known by Bio-Formats as with the original metadata, but clients will need to be modified for the larger change.

To test:
 * `touch /tmp/comp.fake`
 * `echo series=1001 >> /tmp/comp.fake.ini`
 * `bin/omero import /tmp/comp.fake`
 * Check that the following is printing in the logs:
```
2014-07-22 21:17:26,327 INFO  [    ome.formats.OMEROMetadataStoreClient] (2-thread-5) Batch#1 of companion files
```

/cc @melissalinkert @jburel