DATAREST-354 - General rewrite of the JSONSchema support.

Significant overhaul of the JSONSchema support. This currently adds the following features:

- Complex nested types are exposed as descriptors with the properties pointing to them whenever necessary.
- Sets are treated as unique collections.
- Enums are handled as expected (enum values are listed).
- Renamings via @JsonProperty are considered.
- @JsonProperty(required = true) is considered and added to required properties.
- Date/time types (legacy Date, JSR-310, ThreeTenBP and Joda Time) are exposed with format "date-time".
- Objects with @JsonValue methods are considered to be rendered as String value.
- Formats and patterns can be manually configured on MetadataConfiguration.

TODOs:

- Implementation polish, JavaDoc
- Automatically inspect ObjectMapper to detect customizations made through Mixins and custom Serializers.

spring-data-rest-core/src/test/java/org/springframework/data/rest/core/domain/jpa/Person.java

@@ -1,3 +1,18 @@
+/*
+ * Copyright 2013-2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 package org.springframework.data.rest.core.domain.jpa;
 
 import java.util.ArrayList;
@@ -5,6 +20,7 @@ import java.util.Calendar;
 import java.util.Collections;
 import java.util.Date;
 import java.util.List;
+
 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.Id;
@@ -15,6 +31,7 @@ import javax.persistence.PrePersist;
  * An entity that represents a person.
  * 
  * @author Jon Brisbin
+ * @author Oliver Gierke
  */
 @Entity
 public class Person {