#58 alternative plot layout strategy

[Uwe Rathmann]

QwtPlotLayout calculates the geometry of its canvas by subtracting the geometries for axes, titles and legend from a given bounding rectangle.

This way it is hard to control the geometry of the canvas, what is necessary for certain situation like when a fixed aspect ratio between height/width is required - or when aligning plots in grid layouts.

To solve these type of plots a different type of layout strategy would be helpful, starting with a given geometry of the canvas aligning the rest to it.