Bug 914100 - [Messages] Prevent keyboard from disappearing when recipients are rendered after user input

- Recipients.View
    - Had a race condition between `render()` and `focus()` because of calls to `innerHTML` within `render()` (and `target.isPlaceholder`?) which were asynchronous
    - Used `setTimeout` in 3 places to defer setting focus to the next execution turn to allow recipients list rendering to complete
- Tests:
    - Integration test needed?
- Questions:
    - This now fixes three cases of the keyboard hiding:
        - when adding recipients by typing ';'
        - when deleting manually entered contacts
        - when deleting contacts entered from the contacts app.
    - However, the keyboard *still* hides when you are adding recipients from the contacts app, because that gets handled by `Recipients.prototype.add`, which calls `render()` at the end, but not `focus()`. This may be desired behavior when you are generally adding from contacts app, or maybe not.  I suggest adding a `focus()` here as well.  Waiting for review to decide.