Update Batch Documentation to Better Reflect Purpose of the First Email

[carrickr]

The first email you get from batch has a succeed/fail based on:

• The collection referenced on the spreadsheet exists
• The email on the spreadsheet is a user in Avalon and has rights to the collection
• The spreadsheet is in the overall proper format (proper headers, etc)

Individual rows are not validated at this time, that's handled when the second email fires.

We should update the batch documentation to make it clear that getting a success case for the first email does not mean every row is valid. Also perhaps change the wording in the email.

[phuongdh]

I think it's better to also update the email to avoid misleading users