Add Jackson 2 HttpMessageConverter and View

Jackson 2 uses completely new package names and new maven artifact ids.
This change adds Jackson 2 as an optional dependency and also provides
MappingJackson2HttpMessageConverter and MappingJackson2JsonView for use
with the new version.

The MVC namespace and the MVC Java config detect and use
MappingJackson2HttpMessageConverter if Jackson 2 is present.
Otherwise if Jackson 1.x is present,
then MappingJacksonHttpMessageConverter is used.

Issue: SPR-9302

build.gradle

@@ -327,6 +327,7 @@ project('spring-web') {
         compile("commons-httpclient:commons-httpclient:3.1", optional)
         compile("org.apache.httpcomponents:httpclient:4.1.1", optional)
         compile("org.codehaus.jackson:jackson-mapper-asl:1.4.2", optional)
+        compile("com.fasterxml.jackson.core:jackson-databind:2.0.1", optional)
         compile("taglibs:standard:1.1.2", optional)
         compile("org.mortbay.jetty:jetty:6.1.9") { dep ->
             optional dep