Added WuQwtPlot that extends QwtPlot and adds a signal for display of a context sensitive (right-click) menu that includes the event and the X and Y-coordinates in the graph that correspond to the location of the mouse click.
Implement part of WB-405 Easier options for setting of palette thresholds: If thresholding is enabled, the user can right-click the mouse on the histogram plot that results in a menu popping up that allows the user to set either the low or high threshold using the X-coordinate of the mouse on the histogram plot.
Added link icon that will be used in GUI for linking threshold low and high controls.
Bug Fix: If image capture failed, the graphics state, prior to attempted image capture, was not properly restored.