Minor screenrc cleanup

- Inspired by
  https://github.com/sorin-ionescu/dotfiles/blob/master/screenrc

-  Set the escape sequence to CTRL+\.
Some ctags experiments
Track Symbola
Tmux, set \ as prefix key
Start tmux index @ 1, not 0
Generic wallpaper name
Tmux revamp
Sensible status bar
Set clock mode to 12 hour
Sensible tmux window highlighting