PDI-10762 - Trans and TransMeta leak

1) For empty constructors for Trans and TransMeta classes assign
LogChannel.GENERAL chanel by default.
2) junits to check LogChanel.GENERAL added
3) LoggingRegistry now thread-safe singlton class
4) added junit test to test that LoggingRegistry is statically initialized
Merge pull request #487 from prakapenka/PDI-10762

PDI-10762 - Trans and TransMeta leak