Proxying feature

[multiholle]

Add a proxying feature which allows unmatched requests to be forwarded to the actual server. This would allow us to use RESTMock for developing new REST services without the implementation of the REST endpoint on the actual server.

See WireMock for more information: http://wiremock.org/docs/proxying/

[andrzejchm]

thanks for the suggestion, definetely a part of next major release