SelfHosting test: Also try using a relationship.

SelfHosting test: Also try using a relationship.

        * src/main/java/org/glom/web/server/database/DBAccess.java:
        convertResultSetToDTO(): Move some code into a public
method as:
        * src/main/java/org/glom/web/server/SqlUtils.java:
        fillDataItemFromResultSet(): This takes a DataItem and
sets it from a value from a datbase recordset.
        * src/main/java/org/glom/web/server/libglom/Document.java:
Make getDocument() public, so we can use it in a test.
        * src/test/java/org/glom/web/server/SelfHostExampleTest.java:
Add testExampleMusiccollectionDataRelated() and call it from
        testExampleMusiccollectionData(), to do a basic test of using
a relationship.