Batch update by profile hard limited to 9 profile fields

Marking this for the sprint per discussion with Dgg - removing the limit is easy - but some possibility of performance gripes if we do (in previous testing I found the profile code was querying the custom_field table in the db once per row (per field?) BUT that may have changed as it was a while back.

Note that the UI enforces a row limit of 100. I didn't find loading 13 fields with 100 rows especially slow (noticeable time to load but 'acceptable')