Log message

<g:StackLayoutPanel> is now consistent with <g:TabLayoutPanel> and
<g:DisclosurePanel> in its use of <g:header> and <g:customHeader>.

The parsers for StackLayoutPanel, DockLayoutPanel and TabLayoutPanel
now all treat their unit (or barUnit) attributes as optional, and
default them to PX

Also,  yet another pass at making the generator more strict: if any extra
attributes, elements or body text are left after all the parsers are run, the
user is scolded.

	Modify	/trunk/samples/mail/src/com/google/gwt/sample/mail/client/Shortcuts.ui.xml	diff
	Modify	/trunk/user/src/com/google/gwt/uibinder/elementparsers/DockLayoutPanelParser.java	diff
	Add	/trunk/user/src/com/google/gwt/uibinder/elementparsers/IsEmptyParser.java	diff
	Modify	/trunk/user/src/com/google/gwt/uibinder/elementparsers/StackLayoutPanelParser.java	diff
	Modify	/trunk/user/src/com/google/gwt/uibinder/elementparsers/TabLayoutPanelParser.java	diff
	Modify	/trunk/user/src/com/google/gwt/uibinder/elementparsers/UIObjectParser.java	diff
	Modify	/trunk/user/src/com/google/gwt/uibinder/rebind/UiBinderWriter.java	diff
	Modify	/trunk/user/src/com/google/gwt/uibinder/rebind/XMLElement.java	diff
	Modify	/trunk/user/test/com/google/gwt/uibinder/UiBinderJreSuite.java	diff
	Modify	/trunk/user/test/com/google/gwt/uibinder/elementparsers/DockLayoutPanelParserTest.java	diff
	Modify	/trunk/user/test/com/google/gwt/uibinder/elementparsers/ElementParserTester.java	diff
	Add	/trunk/user/test/com/google/gwt/uibinder/elementparsers/IsEmptyParserTest.java	diff
	Add	/trunk/user/test/com/google/gwt/uibinder/elementparsers/StackLayoutPanelParserTest.java	diff
	Add	/trunk/user/test/com/google/gwt/uibinder/elementparsers/TabLayoutPanelParserTest.java	diff
	Add	/trunk/user/test/com/google/gwt/uibinder/elementparsers/UIObjectParserTest.java	diff
	Modify	/trunk/user/test/com/google/gwt/uibinder/elementparsers/UiJavaResources.java	diff
	Modify	/trunk/user/test/com/google/gwt/uibinder/rebind/XMLElementTest.java	diff