MULE-7203: Move ws-proxy from patterns/core into a new web services module

Created mule-module-ws. Moved WSProxy and ws namespace from pattern-core to mule-module-ws. Made pattern-core depend on mule-module-ws so as to keep existing pattern:web-service-proxy element working (using the implementation in mule-module-ws). Moved HttpProxy to mule-transport-http and made mule-module-ws depend on mule-transport-http as WSProxy depends on HttpProxy.