Document: load(), save(): Handle the example rows.

Document: load(), save(): Handle the example rows.

	* src/main/java/org/glom/web/shared/DataItem.java: Add get/setDate()
	and get/setImage().
	* src/main/java/org/glom/web/server/libglom/Document.java:
	load(), save(): Load and save the example rows, though the date, time
	and image types are not handled properly yet.
	* src/test/java/org/glom/web/server/libglom/DocumentTest.java:
	Add testReadTableExampleRows() just to check that something is read.