Ticket0503

Initial design.
Before including to master -> check if {{depth}} can be relative. Example: When being "inside" a branch ("zoom"-mode), {{depth}}, or new variable which indicates depth, should always begin at 0. In branchModel.jst.hbs, class depth-{{depth}} allows to make the left offsets.

This is needed to highlight an entire line if desired, even though notes are nested. Otherwise the background of a note would depend on the padding of its parent(s).