Changed default inclusion setting in Jackson serialization from Include.NON_DEFAULT to NON_EMPTY.

This is because LocalDate and DateTime requests were not sending default values of date:today and datetime:now,
but function calls need to be pure (not dependent on current date/time).
Removed vararg methods because they cannot guarantee type safety.
Published 0.4.3.
Tweaked logging not to waste cycles when logging level is not DEBUG or TRACE.
Logger can now be accessed by resolving an org.slf4j.Logger interface through the ServiceLocator.
Added some safety checks in case of HTTP errors (abort request & close connection).
Fixed order paremeter always starting with &.