Fix the build (mvn package)

Fix the build (mvn package)

	* src/main/java/org/glom/web/shared/libglom/layout/LayoutGroup.java
	(LayoutGroup): Make the LayoutItemList inner class static and protected.
	Otherwise the GWT Java->Javascript compilation fails with just this
	error, during mvn package or when attempting to view in a browser,
	in the GWT developer mode in Eclipse.

	[INFO] --- gwt-maven-plugin:2.4.0:compile (default) @ gwt-glom ---
	[INFO] auto discovered modules [org.glom.web.OnlineGlom]
	[INFO] Compiling module org.glom.web.OnlineGlom
	[INFO]    [ERROR] Errors in 'file:/home/murrayc/checkouts/gnome/gwt-glom/src/main/java/org/glom/web/client/OnlineGlomServiceAsync.java'
	[INFO]       [ERROR] Line 46:  Failed to resolve 'org.glom.web.client.OnlineGlomService' via deferred binding
	[INFO]    Scanning for additional dependencies: file:/home/murrayc/checkouts/gnome/gwt-glom/src/main/java/org/glom/web/client/ui/details/DetailsCell.java
	[INFO]       [WARN] For the following type(s), generated source was never committed (did you forget to call commit()?)
	[INFO]          [WARN] org.glom.web.client.OnlineGlomService_Proxy
	[INFO]    [ERROR] Cannot proceed due to previous errors

	It has taken me 2 days to find out what was causing that. After reducing
	the code, the compiler eventually showed me the full error message.