Provide dependency management for JAXB as it's not provided with Java9 anymore

[snicoll]

To reproduce, build the spring-boot-sample-data-jpa sample (mvn spring-boot:run works fine because we're not forking the process) and run the jar with java 9:

$ java -jar spring-boot-sample-data-jpa-2.0.0.BUILD-SNAPSHOT.jar

Caused by: java.lang.NoClassDefFoundError: javax/xml/bind/JAXBException
	at org.hibernate.boot.spi.XmlMappingBinderAccess.<init>(XmlMappingBinderAccess.java:43) ~[hibernate-core-5.2.12.Final.jar!/:5.2.12.Final]
	at org.hibernate.boot.MetadataSources.<init>(MetadataSources.java:87) ~[hibernate-core-5.2.12.Final.jar!/:5.2.12.Final]
	at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.<init>(EntityManagerFactoryBuilderImpl.java:208) ~[hibernate-core-5.2.12.Final.jar!/:5.2.12.Final]
	at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.<init>(EntityManagerFactoryBuilderImpl.java:163) ~[hibernate-core-5.2.12.Final.jar!/:5.2.12.Final]
	at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:51) ~[spring-orm-5.0.2.RELEASE.jar!/:5.0.2.RELEASE]
	at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) ~[spring-orm-5.0.2.RELEASE.jar!/:5.0.2.RELEASE]
	at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:387) ~[spring-orm-5.0.2.RELEASE.jar!/:5.0.2.RELEASE]
	at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:376) ~[spring-orm-5.0.2.RELEASE.jar!/:5.0.2.RELEASE]
	at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:341) ~[spring-orm-5.0.2.RELEASE.jar!/:5.0.2.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1769) ~[spring-beans-5.0.2.RELEASE.jar!/:5.0.2.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1706) ~[spring-beans-5.0.2.RELEASE.jar!/:5.0.2.RELEASE]
	... 24 common frames omitted
Caused by: java.lang.ClassNotFoundException: javax.xml.bind.JAXBException
	at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:466) ~[na:na]
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:563) ~[na:na]
	at org.springframework.boot.loader.LaunchedURLClassLoader.loadClass(LaunchedURLClassLoader.java:93) ~[spring-boot-sample-data-jpa-2.0.0.BUILD-SNAPSHOT.jar:2.0.0.BUILD-SNAPSHOT]
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:496) ~[na:na]
	... 35 common frames omitted

Adding jaxb or adding the java.xml.bind modules are two options to fix this issue. If the user choses the former, we don't have dependency management and they have to hardcode the version.

[GurinderSinghBrar]

java.xml.bind modules have already been added to spring-boot-parent and spring-boot-samples
pom.xml.

[wilkinsona]

The Platform currently has dependency management for JAX-B 2.3.0 so let's move it over into Boot.