Bug 139986 [CommonNavigator] Convert catch(Error/Throwable) to SafeRunner
In several places the CN framework uses catch(Error/Throwable) to ensure that code does not bring the framework down. Change these to use SafeRunner.
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/extensions/NavigatorContentDescriptorManager.java
if (Policy.DEBUG_EXTENSION_SETUP) {
						System.out.println("Overriding descriptor: " + desc); 
					}
				}
				allDescriptors.put(desc.getId(), desc);
				if (desc.hasSaveablesProvider()) {
					saveablesProviderDescriptors.add(desc);
					if (Policy.DEBUG_EXTENSION_SETUP) {
						System.out.println("Saveables provider descriptor: " + desc); 
					}
				}
				if (desc.isSortOnly()) {
					sortOnlyDescriptors.add(desc);
					if (Policy.DEBUG_EXTENSION_SETUP) {
						System.out.println("SortOnly descriptor: " + desc); 
					}
				}
			}
		}
	}
	/**
	 * 
	 */
	private void computeOverrides() {
		if (overridingDescriptors.size() > 0) {
			NavigatorContentDescriptor descriptor;
			NavigatorContentDescriptor overriddenDescriptor;
			for (Iterator overridingIterator = overridingDescriptors.iterator(); overridingIterator
					.hasNext();) {
				descriptor = (NavigatorContentDescriptor) overridingIterator