[TRUNK-3499] Support more CustomDatatypes and their associated CustomDatatypeHandlers
[TRUNK-3499] removed all un implemented previously overriden methods
[TRUNK-3499] added getValue(...),toHtmlSummary(..) and toHtml(..) to BaseMetadataFieldGenDatatypeHandler
[TRUNK-3499] made some changes to my previous commit
[TRUNK-3499] added BaseOpenmrsDatatype and BaseOpenmrsFieldDatatypeHandler
[TRUNK-3499] made some small change i.e. T extends OpenmrsObject
TRUNK-3499 made some changes according to the previous reviews