Email auth factor (#3602)

* Add email 2fa toggle

* Add UI elements needed for 2fa codes in login

* Wire up to the server

* Give a better failure message for bad 2fa code

* Handle enter key in login form 2fa field

* Trim spaces

* Improve error message

src/state/modals/index.tsx

@@ -107,6 +107,7 @@ export interface PostLanguagesSettingsModal {
 export interface VerifyEmailModal {
   name: 'verify-email'
   showReminder?: boolean
+  onSuccess?: () => void
 }
 
 export interface ChangeEmailModal {