Rewrite UI with prettier callbacks

[milasudril]

Some template currying would make the code much cleaner than implementing multiple interfaces.

Remaining tasks

• [x] Add status bar
• [x] Add record key bindings
• [x] Add fade-in/out key bindings
• [x] Add channel state indicators
• [x] Add application icon
• [x] Do some backdrop to the logo

[milasudril]

WIP in branch rewrite