Polish (minor)
Introduced MvcUriComponentsBuilder to create URIs pointing to controller methods.

MvcUriComponentsBuilder allows creating URIs that point to Spring MVC
controller methods annotated with @RequestMapping. It builds them by
exposing a mock method invocation API similar to Mockito, records the
method invocations and thus builds up the URI by inspecting the mapping
annotations and the parameters handed into the method invocations.

Introduced a new SPI UriComponentsContributor that should be implemented 
by HandlerMethodArgumentResolvers that actually contribute path segments 
or query parameters to a URI. While the newly introduced 
MvcUriComponentsBuilder looks up those UriComponentsContributor instances 
from the MVC configuration.

The MvcUriComponentsBuilderFactory (name to be discussed - MvcUris maybe?) 
prevents the multiple lookups by keeping the UriComponentsBuilder 
instances in an instance variable. So an instance of the factory could 
be exposed as Spring bean or through a HandlerMethodArgumentResolver to 
be injected into Controller methods.

Issue: SPR-10665, SPR-8826
Integrate suggested support for creating MVC URLs

The key contract is MvcUrls. An instance is automatically created with
the Spring MVC namespace and the MVC Java config but can also be easily
created in any configuration.

Some example tests can be found in DefaultMvcUrlsTests.

Issue: SPR-10665, SPR-8826
Polish GenericMessage