Add more convenience methods to PersistenceConfiguration

[hantsy]

trafficstars

I found there only provides a managedClass(Class<?> class) method in the PersistenceConfiguration, but does not provides methods to add a collection of classes.

eg.

PersistenceConfiguration managedClasses(Class<?> classes...)
PersistenceConfiguration managedClasses(Collection<Class<?>> classes)

// add all jpa managed classes in the package located by the specified class
PersistenceConfiguration managedPackage(Class<?> class)
PersistenceConfiguration managedPackages(Class<?> classes...) 
PersistenceConfiguration managedPackages(Collection<Class<?>> classes)