Support RFC6350 calendar properties - FBURL, CALURI, CALADRURI

[spoorun]

Contacts app supports almost all the vCard 4 properties (with issues open for the remaining ones).

The Calendar properties under RFC6350 https://tools.ietf.org/html/rfc6350#page-49 have not been addressed.

Proposal: user can add 'Calendar' as an option from the list of fields, and then they can enter any of the three calendar properties.

FBURL - is a URL which represents information about when the contact is free or busy (can be used for example by other scheduling software)
CALURI - is an address which can be opening to show the Contact's calendar
CALADRURI - is an address (including email address) which a user or software can send a calendar request to

For example, Jane opens a calendar app, creates an event, and invites Ngo and Sam to a meeting. The app sends the invites direct to Ngo and Sam's calendars, using the addresses contained in CALADRURI.

[hamza221]

Can be a continuation #213