Support embedded objects with fields needing (join) table embedded in multiple places

[andyjefferson]

If we have an embedded object with a field of type Set and this stored in a (join) table, we currently only allow this to be stored in a single table. If the embedded object is embedded in multiple different owner classes then we need to support each embedding owner to specify its own join table.

The methods
RDBMSStoreManager.getTable(AbstractMemberMetaData mmd)
RDBMSStoreManager.getBackingStoreForField(ClassLoaderResolver clr, AbstractMemberMetaData mmd, Class type)
RDBMSStoreManager.getBackingStoreForCollection(AbstractMemberMetaData mmd, ClassLoaderResolver clr, Class type)
RDBMSStoreManager.newJoinTable(Table ownerTable, AbstractMemberMetaData mmd, ClassLoaderResolver clr)
are likely the ones needing updates to support this