DbObjectExecutionFixture: simplify if..else.. because only enums used
add classcast to silence warning in OracleEnvironment
make Direction a top-level class
make DbParameterAccessor.javaType private
remove PostgresEnvironment#createAutogeneratedPrimaryKeyAccessor

this method is exactly the same as the superclass method it overwrites
encapsulate more fields in DbParameterAccessor
Merge pull request #143 from benilovj/minor-refactorings-and-cleanup

Minor refactorings and cleanup