Replying, forwarding, avatars sent out of band, trusted badges

Multiple new features:

• Replying to messages.
• Forwarding messages.
• Avatars can now be cropped and sent as URLs.
• Trusted badges: verified account, staff account, danger.
• French translation by @blasius.
• UI refactored for consistency and clarity.
• Multiple bug fixes.

The full list of changes: v0.17.9...v0.18.0