Exclude null requestURI in MHSR.getRequestURL()

This commit undoes the changes made in ec5d81e78e and ensures that the
getRequestURL() method in MockHttpServletRequest does not include the
String "null" for a null requestURI by first checking if the requestURI
contains text before including it in the composed URL.

Issue: SPR-10643
Polish Javadoc in ResourceUtils
Add support for Objenesis proxy creation.

Extended DefaultAopProxyFactory to create Objenesis based proxies if the
library is on the classpath. This allows classes without a default
constructor being CGLib proxied. We're now falling back to original CGLib
based behavior in case the proxy creation using Objenesis fails.

Objenesis 2.0 is now inlined into spring-core to avoid interfering with
other Objenesis versions on the classpath.

Issue: SPR-10594
Merge pull request #327 from olivergierke/SPR-10594

# By Oliver Gierke
* SPR-10594:
  Add support for Objenesis proxy creation.
Add test for StandardReflectionParameterNameDiscoverer

Added test to StandardReflectionParameterNameDiscoverer that
demonstrates discovering of parameter names on an interface.

Issue: SPR-9643
AbstractBeanFactory removes alreadyCreated entry after bean creation failure

Issue: SPR-10896
EhCacheFactoryBean calls addCache after listener registration

Issue: SPR-10904
Fixed javadoc references