Bug 287139 [CommonNavigator] Add core expression to determine initial activation for NCE
Build ID: 20090619-0625 Steps To Reproduce: Currently, the definition of the Navigator Content Extension via plugin.xml allows to specify the boolean attribute allowByDefault which controls if the contributed content is active by default. It makes sence to change the type of the attribute from boolean to core expression, which will allow to evaluate the default context and show content depending on it. This will ease the control of content and enhance the declarative configuration of CNF and NCEs. More information:
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/navigator/INavigatorContentDescriptor.java
String getSuppressedExtensionId();
	/**
	 * @return Returns the overridePolicy or null if this extension does not
	 *         override another extension.
	 * @since 3.4
	 */
	OverridePolicy getOverridePolicy();
	/**
	 * @return The descriptor of the <code>suppressedExtensionId</code> if
	 *         non-null.
	 */
	INavigatorContentDescriptor getOverriddenDescriptor();
	/**
	 * 
	 * Does not force the creation of the set of overriding extensions.
	 * 
	 * @return True if this extension has overriding extensions.
	 */
	boolean hasOverridingExtensions();
	/**
	 * @return The set of overriding extensions (of type
	 *         {@link INavigatorContentDescriptor})
	 */
	Set getOverriddingExtensions();
	/**
	 * @return true if the extension's content provider may adapt to a {@link SaveablesProvider}.
	 */
	boolean hasSaveablesProvider();
}