Ui design: improving the look & feel (issue inviwo/inviwo-dev#726)
Ui design: improving the look & feel (issue inviwo/inviwo-dev#726)

* changed dockwidget title style in connection with custom titlebar for InwivoDockWidget (issue inviwo/inviwo-dev#351)

* changed menu color scheme

* fixed Scrollbars

* updated Sliders to grayscale


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