Templates

Sending the PR to get initial feedback.
That's just a stub, don't merge it.

I would like to merge into this also this https://github.com/emanuele45/Dialogo/commits/theme_playing branch (or something along the lines) and give add-ons a much better control over layers in the template.

Opinions and suggestions are welcome! :dancers: 

@eurich because he will probably not receive the notification (while I know Spuds and Norv will receive it :smiling_imp: