STPlotEditor now inherits from STEditor. This class is still a basic sketch, lots to implement later.
Added signals addVariableClicked() and editPlotClicked() to STPlotWidget. When the user right clicks on the plot widget, the options to add a variable or edit the plot are displayed, the signals are emitted when a selection is made.
Successfully set the STVariableCollection as the model for the QListView in STVariableCollectionEditor.
Connect statements have been added to respond to the two new STPlotWidget signals: toAddVariable() and toEditPlot(). In the former, a simple QInputDialog appears and allows the user to enter a PV name. The supplied name is then added to STVariableCollection. In toEditPlot, an instance of STEditorDialog appears with the STPlotEditor displayed.