TRUNK-5822: Switch FormField domain from hbm.xml to JPA annotations

[pidsonn]

Description of what I changed

Issue I worked on

see https://issues.openmrs.org/browse/TRUNK-5822

Checklist: I completed these to help reviewers :)

• [x ] My IDE is configured to follow the code style of this project.

  No? Unsure? -> configure your IDE, format the code and add the changes with git add . && git commit --amend

• I have added tests to cover my changes. (If you refactored
  existing code that was well tested you do not have to add tests)

  No? -> write tests and add them to this commit git add . && git commit --amend

• [ x] I ran mvn clean package right before creating this pull request and
  added all formatting changes to my commit.

  No? -> execute above command

• [ x] All new and existing tests passed.

  No? -> figure out why and add the fix to your commit. It is your responsibility to make sure your code works.

• [ x] My pull request is based on the latest changes of the master branch.

  No? Unsure? -> execute command git pull --rebase upstream master

[pidsonn]

Updated the branch and #5549 is ready for checking.

[dkayiwa]

Did you see the build failure?