Restore image field mapping in dozer config

* Restored the initial mapping and instead changed the data type
of GetDropDTO#image to java.lang.string. There is no need to
encapsulate the url of the drop image in an image object
Fix invalid parameter index

* The dateAdded parameter is at position 3; not 2
Merge pull request #3 from ushahidi/fix-dozer-mapping-config

Fix dozer field mapping error.