Add gwt-slf4j to errai-jpa-client
Change errai-jpa-client print calls to slf4j log calls
Add GWT Logging to JPA.gwt.xml
Create JPA test parent class that loads GWT logging module
Inherit and configure gwt logging in JpaTest.

This will allow apps using errai-jpa to have their own logging
configurations.
Move client logging dependencies/modules to errai common
Minor change (log level of message in jpa test)