Server Quota Notices in Riot

[manuroe]

element-hq/riot-meta#213

Implement this: https://www.figma.com/file/MYGeFa5VuuB1PC7BknJE1r0j/HHS-Server-Notices-Riot-Mobile-(Android).
It may be required to have a look at web UI: https://www.figma.com/file/G2WhEpAyGVbJ0ZQ9GgjcnbQL/HHS-Nagbar?node-id=0%3A1

• Error on /login
• ([ ] Error on message send) <- skipped because we have only one banner on mobile apps (instead of 2 on riot-web). The nagbar will overlay this message
• Error on /sync
  • Hide text composer in that case
• Recognise server notices room(s) and put them in the dedicated section
• Banner for people who haven't been locked out

[bmarty]

Replace by #2547 for the next steps