Floating history graph

[caladrien]

It would be nice to have a floating history graph. Let me explain:

Most clearly it becomes with solar graphs. Eighter for PV production or solar heating systems. Sun always shines only during the day. In history graphs showing content from the night is not meaningful. For that it would make sense to create an interval for hours_to_show. Could look like hours_to_show: 06:00-18:00
Before that time (6:00) the graph from yesterday in this interval is shown. After the time the diagram starts to unfold with x growing dynamically until the end of the interval.

Information before 5:00 is meaningless but floats the graph unnecessarily.