(core) Enable MFA configuration (and add SMS)

Summary:
Enables configuration of multi-factor authentication from the
account page (for users who sign in with email/password), and adds
SMS as an authentication method.

Test Plan: Project, browser and server tests.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D3215

app/client/ui2018/IconList.ts

@@ -66,6 +66,8 @@ export type IconName = "ChartArea" |
   "Log" |
   "Mail" |
   "Minus" |
+  "MobileChat" |
+  "MobileChat2" |
   "NewNotification" |
   "Notification" |
   "Offline" |
@@ -177,6 +179,8 @@ export const IconList: IconName[] = ["ChartArea",
   "Log",
   "Mail",
   "Minus",
+  "MobileChat",
+  "MobileChat2",
   "NewNotification",
   "Notification",
   "Offline",