#38 New filter option

[Phantomas]

It would be nice if you could add a new filter possibilty
which filters out mails depending on a subject in
connection with and attachment.

Example:

If a mail has the subject "hey" in connection with an
attachment it should be marked as spam or directly
deleted from server.

Another example:

If a mail has the subject "stolen" and has a filesize
between 30000 bytes and 42000 bytes then mark this
mail as spam or delete it directly from the server.