adds select distinct to query

src/main/kotlin/unibz.cs.semint.kprime/domain/dql/Select.kt

...bz.cs.semint.kprime/usecase/common/SQLizeSelectUseCase.kt

....cs.semint.kprime/usecase/common/UnSQLizeSelectUseCase.kt

src/test/kotlin/unibz.cs.semint.kprime/domain/QueryTest.kt

...unibz.cs.semint.kprime/usecase/SQLizeCreateUseCaseTest.kt

...nt.kprime/usecase/serialize/XMLSerializerChangeSetTest.kt

...int.kprime/usecase/serialize/XMLSerializerDatabaseTest.kt