Implement @org.jboss.ws.api.annotation.WebContext support for POJO endpoints

We support @WebContext on EJB endpoints now.
Since Servlet 3.0 spec allows web deployments
without web.xml it is worth to support this annotation
also on POJO WS endpoints.
There are however two restrictions that must be ensured.
If there are multiple WS endpoints in web archive
all annotated with @WebContext annotation then the following
restriction must apply:

• contextRoot value must be the same for all @WebContext annotated endpoints
• virtualHost value must be the same for all @WebContext annotated endpoints
• if there's provided jboss-web.xml or jboss-webservices.xml with context root in deployment
  this DD driven context root will have higher priority than context root specified in annotations.