refactor layouting code

[wirew0rm]

goals/current problems

• reduce hierarchy depth
  • prevent layout/rendering loops caused by resizing during rendering
• increase flexibility (allowing e.g. 3D axes/plots)
• some size computations are currently performed in the render step (mainly computation of axis labels and size)
• tick computations are performed in the rendering step of the axes, but the grid is drawn before the axis (Major Grid lines sometimes don't update on DataSet updates that change the axis range of a chart  #410)
• correctness: currently the axes and charts rendered are not always consistent in every render loop, which is inconvenient for exporting images of the rendered chart => after the render step is completed, the display should be consistent. (There might be things like clipped/overlapping text until the next repaint if it is not preventable, but the data should be correct.)

current state

scenegraph

implementation

• use a single canvas as the root element to also allow for 3D plots and allow more flexible axis types?
  • most chart elements already use a canvas and some sort of coordinate transform
  • would need to implement custom mouse event handling
  • would decrease the usefulness of common javafx tooling?
  • extensibility with standard controls?
• use a custom layouting container which computes the positions of all chart elements in a flat hierarchy
• first compute data ranges from renderers in layout step, then compute axes ticks, then render charts and axes

... to be extended/discussed further

[wirew0rm]

solved by #592, more details and discussions in #579