[RFC] : Filters <-> Mailboxes association

[Emmanuel <e allaud wanadoo fr>]

	Hi all,
answering to Melanie (about using filters to automatically purge the trash
can), I thought a bit more about filters <-> mailbox association. Here is
what I think, I would like comments, hints ...

In general we should be able to associate filters (among all available
filters) to any mailbox (by adding a config string for mailbox containing a
vector of filters name).

"Automatic run of filters" would be limited to special mailboxes : 
	* Inbox : the associated filters would run on incoming mails
	* Trash : the associated filters would run when Balsa exits (this
way you can implement the automatic purge of trash can or whatever).

Bye
Manu