Bug 150593 Enhancements for ResourceManager
The attached patch addresses the following in ResourceManager - Fixes several JavaDoc bugs - Adds a "getImage" method that implements the common pattern of "return existing image if known, or allocate a new image otherwise"
bundles/org.eclipse.jface/src/org/eclipse/jface/resource/ResourceManager.java
* 
     * @since 3.1
     *
     * @return a default image that will be returned in the event that the intended
     * image is missing.
     */
    protected abstract Image getDefaultImage();
    /**
     * Undoes everything that was done by {@link #createImage(ImageDescriptor)}.
     * 
     * @since 3.1 
     *
     * @param descriptor identifier for the image to dispose
     */
    public final void destroyImage(ImageDescriptor descriptor) {
        destroy(descriptor);
    }
    /**
     * Allocates a color, given a color descriptor. Any color allocated in this
     * manner must be disposed by calling {@link #destroyColor(ColorDescriptor)}, 
     * or by an eventual call to {@link #dispose()}. {@link Color#dispose()} must
     * never been called directly on the returned color.
     * 
     * @since 3.1 
     *
     * @param descriptor descriptor for the color to create
     * @return the Color described by the given ColorDescriptor (not null)
     * @throws DeviceResourceException if unable to create the color
     */
    public final Color createColor(ColorDescriptor descriptor) throws DeviceResourceException {