remove custom theme
remove buttons and refactor to use menus
write a more descriptive RainwaveException.getMessage()
add "authentication required" message if anonymous user tries to use playlist
split ActionTask into three proper classes
remove explicitly set gradient background
remove QR icon; use text button with "Scan"
fix small bugs

- Clear user info when clearing preferences
- Check that stations are set before starting stream
Merge branch 'feature/theme' into develop