[MIG-78] Added [--parallelizer (-p)=[parallelizer]] command line option, which is for parallelization strategy name. Allowed value is either table.level (default), row.level or fully classified class name of a custom parallelizer implementing com.nuodb.migrator.backup.loader.Parallelizer. Table level strategy enables 1 worker thread per table at max, while row level enables forking with more than 1 thread, where the number of worker threads is based on the weight of the loaded row set to the size of loaded tables. Notice row level forking may introduce reordering (and typically does it) of the rows in the loaded table.