Clarify transfer behaviour when adding multiple directories from the dashboard using the Add button

[uofmsean]

Version of the documentation
1.16.0

Page (and section, if applicable) where the issue occurs
A few places that could use clarification:
Transfer Tab - "Selecting a directory and clicking Add adds the directory of materials to the transfer."
Transfer Permissions - "Depending on the exact permissions setup, you may be able to add the directory to your transfer, but the transfer will never start."
Start a Transfer - "The transfer name will become the name of your AIP, so make sure that the name is meaningful.", "...so that it is highlighted and click Add."

Description of the issue
There needs to be clarification on the behaviour when multiple directories are added to a transfer using the Add button for each directory. The directories are not "added" to a single transfer but instead will launch a separate transfer for each added directory, and automatic transfer names are generated by taking the entered transfer name and appending "_N" to the transfer names other than the first transfer (where N is a number starting at 1).

Suggested fix
In the sections pointed out above (and potentially other sections), clarify that the Add button (when used with basic transfers) is really adding a new transfer and that subsequent transfer names other than the first will have the "_N" extension for uniqueness. Another possible wording change would be to use something like "sets the directory for the transfer" rather than "adds the directory to the transfer".
In the Basic Transfers section, maybe highlight the importance of the existing text "With the exception of zipped bag transfers, Archivematica requires that all of the materials in the transfer are contained within a top-level directory." and make reference to what happens if you use the dashboard Add button to add multiple directories which simply starts separate transfers.

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