REST related mods that use web.xml

merge changes required to load a web.xml and application named in the web.xml. Currently web.xml is hardcoded in ServingLayer.java but should probably be specified via a config param.
It turns out we do not need a web.xml but do need an @ApplicationPath. We also need to instantiate a ContextConfig class in the ServingLayer (even though the ContextConfig never sets a default webxml file). If we bundle one Application with an @ApplicationPath things just work. I'll submit a new PR with corrections in the various pom's and only one Application with a @ApplicationPath. BTW, I tried removing @ApplicationPath and tried to define the application path in a web.xml - according to the jersey user guide sec 4.7.2.3.2 (https://jersey.java.net/documentation/latest/user-guide.html#d0e3269) this should work if you use a web.xml - however w/o the @ApplicationPath the application was never loaded. I think we need to test this outside of tomcat (w/ grizzly and other JAX-RS compliant servers) to see other behaviors. The remaining issue then is to define projects/build in such a way that only one application (w/ an @ApplicationPath) is loaded. We can discuss all the above idiosyncracies ...