Add html output format for mail annoucement

We want to use a custom annoucement template wich is a HTML template to get a better look into our mail.
No pb to do this except the output format is hardcoded into PLAINTEXT into plugin.

Can you add an option into the plugin configuration (after <templateDirectory> tag for example) to specify the output type (HTMP or PLAINTEXT).
The default should be "text/plain".

The Hardcoded feature is in file ProjectJavamailMailSender.java (svn rev 553871) line 181.

Thx
Christophe