Splits gateway RSocket support in to Common, Client and Broker Modules

Metadata moved to common module. Auto config sets up metadata parsing.
Client module created with properties and helper classes for ease
of using RouteSetup and Forwarding metadata.

src/checkstyle/checkstyle-suppressions.xml

@@ -28,4 +28,5 @@
 	<suppress files=".*Route\.java" checks="FinalClass"/>
 	<suppress files=".*HystrixGatewayFilterFactory\.java" checks="AvoidNestedBlocks"/>
 	<suppress files=".*WellKnownKey\.java" checks="JavadocVariable"/>
+	<suppress files=".*MetadataEncoder\.java" checks="JavadocMethod"/>
 </suppressions>