1.1.3dev: New notification API and interfaces (see #3517)
* `INotificationDistributor`: For pluggable notification distribution channels
* `INotificationFormatter`: For customized notification message formatting
* `IEmailAddressResolver`: For finding email addresses
* `IEmailDecorator`: For adding email headers independently from message formatting 

Implementations for email distribution and ticket notification formatting replace the `TicketNotifyEmail` class hierarchy.

Based on the Announcer plugin. Thanks to everyone who contributed!


git-svn-id: http://trac.edgewall.org/intertrac/log:/trunk@13454 af82e41b-90c4-0310-8c96-b1721e28e2e2