CAY-1946 cdbimport improvments

Basic cdb import improvement: use db merge if model already exist
1) added DbLoaderConfiguration class; this class responsibility should be provide to DataLoader all necessary information
2) DbImportAction - this class will check availability of dataMap file and do merge if it is exist otherwise just load model from db
3) DbImportParameters - was renamed to DbImportConfiguration and also responsible fo construction of necessary objects for during import process
4) functional or end-to-end test for maven plugin basic usage scenarios
5) XmlUnit - for xml file comparison