Bug 263207 [CommonNavigator] Improve DnD tracing and add DnD test suite
There are no DnD tests for the Common Navigator. Also, the CNF has many test utility classes (basically stolen from JDT), these should be moved into a lower level area, and it looks like org.eclipse.ui.test.harness is a good place. (Perhaps we can get the JDT to use these identical versions as well so there is only one copy that everyone uses). Finally, the DnD tracing needs to be improved to show more information and show it more concisely.
tests/org.eclipse.ui.tests.navigator/src/org/eclipse/ui/tests/navigator/DisplayWaiter.java
* not met, then transitions to <code>nextState</code>.
	 * 
	 * @param possibleStates the allowed states
	 * @param nextState the state to transition to
	 */
	private void checkedTransition(int possibleStates, int nextState) {
		assertStates(possibleStates);
		Logger.global.finer(name(fState) + " > " + name(nextState)); 
		fState= nextState;
	}
	
	/**
	 * Implements state consistency checking.
	 * 
	 * @param states the allowed states
	 * @throws junit.framework.AssertionFailedError if the current state is not
	 *         in <code>states</code>
	 */
	private void assertStates(int states) {
		Assert.assertTrue("illegal state", isState(states)); 
	}
	/**
	 * Answers <code>true</code> if the current state is in the given
	 * <code>states</code>.
	 * 
	 * @param states the possible states
	 * @return <code>true</code> if the current state is in the given states,
	 *         <code>false</code> otherwise
	 */
	private boolean isState(int states) {