change type of complex test item builder to long
import ids on refs
numeric index
move content
add explicit guava dependency
add visitor pattern
add Id type
add abstract content store
minor model changes
add EntityType to ParentRef
add ForwardingContentStore
add PersistenceModule interface
move Topic into topic package
remove old unused Identifiable interface
add Topic persistence interfaces and abstract implementations
Add TopicStore to PersistenceModule interface
Attribute/Query clean up
add aliases attributes
add index interfaces
add standard dependencies