Blocked user's cookie setup

[MrOrz]

This is part of the 2nd milestone of user blocking mechanism.

• Loads blockedReason in AppLayout and set cookie isUserBlocked if blockedReason persists
  • Once the cookie is set, there is no way to clear the cookie, unless they use devtools.
• useIsUserBlocked() hook can read if the current browser is owned by blocked user both on browser & during server-side render
• Logging out does not clear isUserBlocked cookie, thus the value is persisted

[coveralls]

Coverage remained the same at 75.363% when pulling abba9a8 on block-user-cookie into 9a68c27 on master.