[kronolith] make participant e-mails optional

[Jens-U. Mozdzen]

Hi,

I'm scheduling a meeting and adding participants that are known in the  
address book, including e-mail. But as I know that some of these  
prefer clear-text emails over generated notifications, I'd like to  
omit sending invitation e-mails to those few.

Can I somehow select which participants to send a notification and  
whom not? It's not about a general setting (i.e. in the address book),  
but per appointment.

Regards,
Jens