ENH: Example how to use dynamic properties and stylesheets

[Punzo]

Bare bones example how to use dynamic properties and stylesheets in CTK to replace QPalette hard coded colors.

This would allow slicer customizations to replace the colors by simply defining them in the styleSheet.

Reference: commontk#1201

[Punzo]

hey @sjh26, @lassoan @jcfr @pieper this is just an bare bones example how we could modify CTK color dynamic changes. I would appreciate a lot if you can provide feedback. Then if you agree on a solution, I can apply the solution to all the CTK classes that uses the QPalette.