Window and Level values always rounded to integer

[tomdoel]

The UI will round the window and level values entered in the text boxes to the nearest integer. For most Dicom images this is the preferred behaviour; however when dealing with images of floating point values it might be desirable to set a non-integrer value.

May require changes to:

• MimPluginLabelEditBox
• MimPluginLabelSlider
• MimViewerPanelToolbar
• MimViewerPanelCallback:ModifyWindowLevelLimits and consideration of how the window/level values affect other parts of the codebase