Add support for showing that attachments were added to the mail

This patch will create an unordered list of mail attachments on a mail log view, if that email has attachments.
hope this will be helpful.

Shouldn't we give the attachments field an unlimited cardinality? Then each attachment filename is stored separately, making the implode / explode operations unnecessary. Probably the custom formatter as well then, since we can just render the field values as is.

The attachment field cardinality is set to unlimited now.

Re-rolling the patch #4 as it started failing after the recent release 1.2.0.