#5 Support repositorycode and apply custom format to email addr

[Guido Leenders]

It helps our software development process if we could:

1. Use a custom format token in the MailTo EMailAddress. Example: pjt-#repositoryCode#@invantive.com
2. Be able to determine solely the repositorycode instead of the full physical path as provided by #repository#

Reason behind this:
We have a repository per application.
On creation of repository XYZ, a mail group is created: pjt-XYZ@invantive.com.
On every checkin on repository XYZ, the mail group receives the differences.

It eases the maintenance of the subversionnotify.cfg, if we could use the repository code in both subject and mailto.