Introduced ResponseProcessorFactory and DefaultResponseProcessorFactory, refactoring the static foreign methods of ResponeProcessor into DefaultResponseProcessorFactory.  This is the first step in moving toward a pluggable serialization model.
Changing names and repackaging serialization functionality a bit--DefaultJsonProcessor to JacksonJsonProcessor, DefaultXmlProcessor to XstreamXmlProcessor.
Introduced GsonResponseProcessorFactory, adding GSON as an optional dependency in the POM. Re-introduced GSON-based serialization classes from RestExpress 0.8.2 to make them pluggable, if desired instead of Jackson.
Updated snapshot version to 0.10.5
Updated common and core pom files to match parent version.
Renamed ResponseProcessorFactory to SerializationProvider, along with implementors DefaultResponseProcessorFactory (to DefaultSerializationProvider) and GsonResponseProcessorFactory (to GsonSerializationProvider).