android上的DataNucleus：合并来自api-jpa，rdbms和核心jar的plugin.xml。创建EntityManagerFactory时出现运行时错误：
Caused by: org.datanucleus.exceptions.NucleusException:
Error creating handler of type "persistence" for metadata parsing :
MetaData handler plugin "persistence" was not found.
Please check your CLASSPATH and plugin specification.
at org.datanucleus.metadata.xml.MetaDataParser.parseMetaDataStream(MetaDataParser.java:276)
at org.datanucleus.metadata.xml.MetaDataParser.parseMetaDataURL(MetaDataParser.java:144)
at org.datanucleus.metadata.MetaDataUtils.parsePersistenceFiles(MetaDataUtils.java:863)
at org.datanucleus.api.jpa.JPAEntityManagerFactory.getPersistenceUnitMetaDataForName(JPAEntityManagerFactory.java:1316)
at org.datanucleus.api.jpa.JPAEntityManagerFactory.<init>(JPAEntityManagerFactory.java:410)
at org.datanucleus.api.jpa.PersistenceProviderImpl.createEntityManagerFactory(PersistenceProviderImpl.java:104)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:79)