MONDRIAN-1771 - adding extension point for JdbcSchemaFactory
MONDRIAN-1771 - adding second point for getting the SegmentLoader.  making loadImpl protected so it can be overridden
Merge branch 'mongolap' into MONDRIAN-1771
Merge pull request #190 from kurtwalker/MONDRIAN-1771

MONDRIAN-1771 - adding extension point for JdbcSchemaFactory, additional point for segment loader.