Import text/calendar mime types from an IMAP message to the calendar

[jasonmunro]

Add a "add to calendar" link to the imap message view when the message contains a text/calendar part. The link should convert the calendar to our internal format and add it to the calendar events.

[jasonmunro]

Support for recognizing IMAP messages with a calendar event part is in, and an "add to calendar" link is presented, but we still need to do something when the link is clicked! :)

[dumblob]

Thank you. Important step forwards!

By the way, have you been considering showing directly buttons like yes, tentative, no instead of adding a redirection (first the button add to calendar and yet afterwards once in the calendar application/view the three buttons yes, tentative, no)?

[jasonmunro]

@dumblob, we can absolutely support yes/tentative/no in this case (I think). I have been working on some vCard and iCal format parsing code that I plan to leverage to (eventually) finish this off (along with a pure CalDav calendar module set)!

[marclaporte]

Related: #120