Bug 137917 ImageHandle add setFile method.
According to new Resource Deployment Specification, image builder add a new image type 'File', so ImageHandle should add 'setFile' method as other type methods such as 'setURI'.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ImageHandle.java
List images = targetModule.getListProperty( targetModule,
							Module.IMAGES_PROP );
					if ( images == null || images.isEmpty( ) )
						continue;
					int posn = images.indexOf( image );
					PropertyHandle propHandle = targetModule.getHandle(
							targetModule ).getPropertyHandle(
							Module.IMAGES_PROP );
					assert posn != -1;
					EmbeddedImageHandle imageHandle = new EmbeddedImageHandle(
							propHandle, posn );
					return imageHandle;
				}
				
				
				owner = owner.isVirtualElement( )
						? owner.getVirtualParent( )
						: owner.getExtendsElement( );
			}
		}
		return null;
	}
	/**
	 * Sets the embedded image name that this image refers, if the image source
	 * type is <code>IMAGE_REF_TYPE_EMBED</code>. The reference type is
	 * automatically set in this method. This is not the same as
	 * {@link DesignElementHandle#setName( String )}.
	 * 
	 * @param name
	 *            the embedded image name