Change the default model of the JPA connector from 'Basic' to 'Simple'

A new 'Simple' model was recently added to the JPA storage connector (see DNA-546), and that model is apparently feature-complete and working well. This new model also has solved several issues related to certain JCR functionality (see DNA-546), so it appears to actually be more functional than the 'Basic' model.

The JPA connector's default model should be changed to 'Simple'.