Support registration & login with phone number (#742)

* WIP msisdn sign in

* A mostly working country picker

* Fix bug where you'dbe logged out after registering

Stop the guest sync, otherwise it gets 401ed for using a guest
access token for a non-guest, causing us to beliebe we've been
logged out.

* Use InteractiveAuth component for registration

* Fix tests

* Remove old signup code

* Signup -> Login

Now that Signup contains no code whatsoever related to signing up,
rename it to Login. Get rid of the Signup class.

* Stray newline

* Fix more merge failing

* Get phone country & number to the right place

* More-or-less working msisdn auth component

* Send the bind_msisdn param on registration

* Refinements to country dropdown

Rendering the whole lot when the component was rendered just makes
the page load really slow, so just show 2 at a time and rely on
type-to-search.

Make type-to-search always display an exact iso2 match first

* Propagate initial inputs to the phone input

* Support msisdn login

* semicolon

* Fix PropTypes

* Oops, use the 1qst element of the array

Not the array of object keys which has no particular order

* Make dropdown/countrydropdown controlled

* Unused line

* Add note on DOM layout

* onOptionChange is required

* More docs

* Add missing propTypes

* Don't resume promise on error

* Use React.Children to manipulate children

* Make catch less weird

* Fix null dereference

Assuming [0] of an empty list == undefined doesn't work if you're
then taking a property of it.

src/components/views/elements/AccessibleButton.js

@@ -27,8 +27,8 @@ import React from 'react';
 export default function AccessibleButton(props) {
     const {element, onClick, children, ...restProps} = props;
     restProps.onClick = onClick;
-    restProps.onKeyDown = function(e) {
-        if (e.keyCode == 13 || e.keyCode == 32) return onClick();
+    restProps.onKeyUp = function(e) {
+        if (e.keyCode == 13 || e.keyCode == 32) return onClick(e);
     };
     restProps.tabIndex = restProps.tabIndex || "0";
     restProps.role = "button";