Tracer Model P1 - independent plot axes control

[pullmonkey]

Right now in Param Image Model - X and Y are selected at the top to be represented by the single plot.
In Tracer Model - we have > 1 plots, therefore, the X and Y axes of each plot will need their own selectors.

Remove the global selector.
For each plot, have a selector for X and a selector for Y.

[lustrousgorilla]

Done. State is bookmarked and retrieved per plot. Disabled table variable selection until a 'selected plot' feature is implemented which will allow for the necessary 1-to-1 mapping.