[NONE] Add hovering support to the DOT Editor for the dot color values.

- Provide custom implementation of the DotEObjectHover and
DotHoverProvider (with corresponding bindings into the DotUiModule) to
show the detailed color description when hovering over the current dot
color values.
- Implement corresponding DotHoverTests test cases.

org.eclipse.gef.dot.tests/src/org/eclipse/gef/dot/tests/AllUiTests.java

@@ -28,7 +28,7 @@
 		DotContentAssistTests.class, DotBSplineInterpolatorTests.class,
 		DotHtmlLabelTests.class, DotOutlineViewTests.class,
 		DotFoldingTests.class, DotStyleTests.class, DotRecordLabelTests.class,
-		DotAstTests.class })
+		DotAstTests.class, DotHoverTests.class })
 public class AllUiTests {
 
 }