Make "Propertional" an axis-specific setting

[ghorwin]

Move Chart-option "Proportional" to axis with the following meaning:

-> only available for coordinate-coordinate-charts (colormap plots)
-> when enabled means: axis aligns its scale to other axis

-> autoscale off + disabled for current axis
-> min value enabled and editable
-> max value disabled (value is automatically determined)

-> turning "propertional" on, disables "proportional" of other axis