Added AggregationVisitor to retrieve group by
Modified SQLQueryTranslator to use ParsedQuery instead of QueryTree
changing mapping analyzer to use ParsedQuery
Modifying MappingAnalyzer to use JSQLParser
Added comment to the SQLparser classes
modified selection and projection to work with a single expression
instead of list.
Add implementation for MetaMappingExpander and MappingParser
Added set selection for the ParsedQuery