End-to-end encryption: room messages (receiving)

[bradlegge]

Need to distinguish messages which are:

• Unencrypted (white background?)
• Encrypted but from an unverified device (red background?)
• Encrypted from a verified device (green background?)
• Encrypted but you are blocked from receiving (red background + "You are not in recipients" message as contents).

Using background for this sucks aesthetically and is even worse for red/green colourblind folks. Need a better solution.