Add chat and call support in contacts manager.

Added two buttons to chat or call a contact. When clicked the contacts manager is closed to talk or chat with the contact. This feature does not yet support calling/chatting multiple instances of a contact.
The `doCall` and `startChat` scope functions ought to take a contact rather than a userid. Since they're both just passing it into `getContactSessionId`, that function can get the userid itself to simplify things.