Add a size limit to the quarantine digests

[anonymous]

Given that quarantine digests can get quite large, and there's no paging

mechanism for managing large lists in an email digest, it may be necessary to add a user-configurable size limit to the digest feature, letting users specify how many quarantined items they're willing to receive in a digest. If the user's quarantine contains more than that number of items, the digest would be replaced with a short email that explains the situation and provides a link for the user to login to the web interface to manage his quarantine there (where paging mechanisms make large lists manageable).

[mortonda@…]

Trying not to add database schema for 1.0.3, but this would be perfect for implementation after we make the config table vertical as mentioned in #31