End-end encryption: room state / room level privacy indication

[bradlegge]

Need a way to constantly remind users of the current level of privacy within the room.

1. public and unencrypted (grey unlocked padlock?)
2. private and unencrypted (red unlocked padlock?)
3. encrypted but with unverified devices present (red flashing locked padlock?)
4. encrypted but all devices either verified or blocked (green locked padlock?)