ConfiguredDocument: Restore correct addition of hidden primary key items.

ConfiguredDocument: Restore correct addition of hidden primary key items.

	* src/main/java/org/glom/web/client/ui/list/ListTable.java
	(ListTable.createCellTable): Uncomment out the check for the hidden
	primary key.
	* src/main/java/org/glom/web/server/ConfiguredDocument.java: Only
	add primary key items for top-level lists and portals, as before,
	instead of adding them to each group.
	* src/main/java/org/glom/web/shared/libglom/layout/LayoutGroup.java:
	Actually implement the extra methods such as setHiddenPrimaryKey() and
	comment that these are used only for top-level list groups and in portals.
	This strangeness suggests even more that this should not be squeezed
	into the LayoutGroup class.