Support RFC6350 calendar properties - FBURL, CALURI, CALADRURI

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.

Start by locating the contacts field list and the code that handles vCard properties. Add a Calendar option covering FBURL, CALURI, and CALADRURI, then verify that users can enter and save each property and that the values are represented correctly in contacts.