Fx setting popup enhancements (#2479)
    
    * Set min fx settings popup size

    

    * Keep popup dimensions when frame changes

    

    * Correct crash issue with keeping size between frames

    

    * Update fx settings with node change

    

    * Fix shrinking swatch size on empty fx

    

    * Convert Fx Settings to dockable window

    

    * Fixing Travis build error

    

    * Replace FxSettingsPanel with DockWidget

    

    * Set initial switch window dimensions

    

    * Open popup in center of screen