Refactored DefaultServiceLocator to use composition rather than inheritance to support error handling hook

Introduced a NullLoggerFactory which aligns more cleanly with the dependency requirements of the components

Declared content length for checksums to avoid chunked transfer encoding which is troublesome with nginx (HTTP 411)

Simplified VersionConstraint.getRanges() to getRange(), an aggregation of ranges is again a range and the semantics of the aggregation are an impl detail

Made DefaultServiceLocator automatically register Slf4jLoggerFactory if slf4j-api is found on the classpath

Improved support for named loggers by introducing a LoggerFactory component that the other components can use