Nickname feature

[tonygentilcore]

From @aza on October 19, 2016 8:31

• Add menu item to identity actions (e.g., the action sheet upon long-hold of an identity)
• Open a text input sheet (a la identity/channel name screen) and get the value back
• Store json data on the user's account (i.e., a map of GUIDs to nicknames)
• Give the mapping to the client

Copied from original issue: other-xyz/time-cone#136

[tonygentilcore]

We can do this in purely other.js after we can:

1. Persist feature data: https://github.com/other-xyz/courier/issues/186
2. Support chat complete actions: https://github.com/other-xyz/other.js/issues/18

[tonygentilcore]

From @aza on November 4, 2016 16:50

And also, a way for user to input a new name (and hence a way for other.js to prompt).