Share contact ui

[vranki]

As far as I know, there is no ui for sharing a contact to another. The only way to share a contact is to find contact's id (#2756 is related) and copy-paste it in a message. This is way too difficult.

Sharing could be initiated for example from user's info page and/or long press context menu anywhere.

(I'm surprised to see there's no issue for this yet. At least I couldn't find one)