Upgrade Linearized Fits

[butler]

Currently linearized fits are quite un-intuitive and awkward. One needs to perform two steps in the following order

1. click on plot menu and choose "Change Scale" and change the axis scaling (log, linear, y*x etc.) then exit.
2. Click again on plot menu and choose "Linear Fit" set the range and fit.

Further the range is set in units of the scale. So if ln(q*I) then lower limit is not qmin but ln(qmin*I(qmin)). Finally there are no lines on the graph to enable a visual review of the range chosen.

The scale functionality can be useful in its own right to visualize in different ways, but it should be decoupled from the linearized fits. The linearized fit panel should allow for choosing the type of fit (or scale) desired and whether to set the range in the original q space or in the scale of the linearized x axis. Finally the range should be graphically shown just as it is in fitting.

A quick and dirty start that goes a long way might be to add a button on the lineraized plots panel to call the scale panel.

[butler]

Turns out (see ticket #590) the whole linearized fit infrastructure consists of 4-5 python modules that are an integral part of the plottools package and launched from the PlotPanel? context menu "Linear Fit". Thus what was suggested above probably means removing this from plottools (where I don't see how it makes any sense for it to live anyway?) and create a new perspective of linearized plots.