Translation review comment

- Hibernate entity and liquibase change log
- UI in gwt for add comment and get comments for a particular trans unit
- tests 
- technical debt found

This feature is now demostrateable. I think the data modal and back end is complete except the technical debt items can be addressed separately. Luke has a new idea on UI but that can go in separately as well.
To see this feature without liquibase permanently written to your mysql database:
* $cd server
* $mvn clean package -Pchrome
* $cd functional-test
* $mvn integration-test -Dfunctional-test -Dcargo.wait
* ...
* $[INFO] Press Ctrl-C to stop the container...
* In you IDE, run ExperimentTest then you can log in as admin/admin