[dovecot] More documentation

I just wrote a bit of documentation. Probably not very well organized, improvement suggestions welcome :)

http://dovecot.procontrol.fi/doc/INSTALL http://dovecot.procontrol.fi/doc/configuration.txt http://dovecot.procontrol.fi/doc/mail-storages.txt

Those are also in the main dovecot.procontrol.fi web page. They also talk about a few features not yet in CVS..