Bug 49117 [Plan Item] Workbench needs hooks for new welcome support
M6 We need to provide an extension point and some interfaces to allow for a primary feature to declare a welcome page. This extension point will be tied the new IProduct being defined by the Core team and needs to have 3 states 1) Fill whole screen 2) Collapsed on the right when the user selects something and starts working 3) Disables when it is no longer of any use
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/IDEWorkbenchAdvisor.java
* Returns the set of versioned feature ids from current session.
	 * 
	 * @return set of versioned feature ids (element type: <code>String</code>)
	 */
	private Set getCurrentFeatures() {
		Assert.isNotNull(currentFeatures);
		return currentFeatures;
	}
	
	/**
	 * Returns the ordered set of versioned feature ids new for this session.
	 * 
	 * @return ordered set of versioned feature ids (element type: <code>String</code>)
	 */
	private Set getNewlyAddedFeatures() {
		Assert.isNotNull(newlyAddedFeatures);
		return newlyAddedFeatures;
	}
	
	/**
	 * Initializes the old, current, and newly added features.
	 */
	private void initializeFeatureSets() {
		Assert.isTrue(currentFeatures == null);
		
			
		IDialogSettings settings = IDEWorkbenchPlugin.getDefault().getDialogSettings();
		String[] previousFeaturesArray = settings.getArray(INSTALLED_FEATURES);
		previousFeatures = null;
		if (previousFeaturesArray != null) {