HSEARCH-1121 Defining new ClassLoadingService and hooking into the service manager.

The class loader service must be provided by the SearchConfiguration.
HSEARCH-1121 Removing deprecated method from ClassLoaderHelper and moving ClassLoaderHelperTest into engine module
HSEARCH-1121 Removing transaction helper. JoinableCMTTransaction does not even exist anymore.
HSEARCH-1121 Cleaning up classloading via ClassLoadingHelper. All classloading needs to occur via the ClassLoaderService.