Spring Boot 2.1 upgrade

* Removed MockBinderRegistryConfiguration
* Move necessary beans from `BindingServiceConfiguration` which is now auto configurable into
  `BinderFactoryConfiguration` that is invoked by `EnableBinding` in order to avoid certain
  cyclic dependency issues. The beans moved are binding target factories of type
  `MessageSourceBindingTargetFactory` and `SubscribableChannelBindingTargetFactory` and their dependencies.
  As a side effect, `ContentTypeConfiguration` is also brought back at the `EnableBinding` level through
  `BinderFactoryConfiguration`.
* Restore `ServerController`  bean in SchemaServerConfiguation as the removal of it
  earlier introduced  some connectivity issues with the schema registry server.
* Update copyrights

spring-cloud-stream-test-support/src/test/java/org/springframework/cloud/stream/test/example/ExampleTest.java

@@ -39,7 +39,8 @@ import static org.assertj.core.api.Assertions.assertThat;
  * correctly.
  */
 @RunWith(SpringJUnit4ClassRunner.class)
-@SpringBootTest(classes = ExampleTest.MyProcessor.class, properties = { "server.port=-1",
+@SpringBootTest(classes = ExampleTest.MyProcessor.class, webEnvironment = SpringBootTest.WebEnvironment.NONE,
+		properties = {
 		"--spring.cloud.stream.bindings.input.contentType=text/plain",
 		"--spring.cloud.stream.bindings.output.contentType=text/plain"})
 @DirtiesContext