introduced setControlParameter and related call tree.

This way it is not required to set the <EmitOnDownPress> for <SliderComposed>
in skins. Its value  was ignores anyway.
switched remaining setControlParameterDown/Up double to setControlParameter
No need for left and right connection in a combobox.
Removed null setControlParameter?Up
removed unused code
removed unused Left/Right dependency in WOverview::mouseReleaseEvent
moved "wheel" connection to WWaveformViewer
Converted COTs to COSs in WWaveformViewer
Make wslidercomposed Button independent
Removed unused and button related m_left/rightConnections from set/resetControlParameter