update comment entity

with:
1. add persistent property -> CommentRecipientType recipientType (enum: PERSON, TEAM, SECTION, COURSE)
2. rename receiverEmail to recipients, with type changed from String to Set<String>
3. add commentAttributesTest and make it green
update commentsDb and make commentsDbTest green
Merge remote-tracking branch 'origin/master' into 72675318
create Permission.java
update logic to support new comment entity and make dev green
update actions to support new comment entity and make dev green
improved Permission.java

also changed the comment in instructor.java
Merge remote-tracking branch 'origin/master' into 72675318
Merge remote-tracking branch 'origin/72675318' into AccessControl
Merge branch 'master' into 72669836

# By franklingu (36) and others
# Via Damith C. Rajapakse (18) and others
* master: (54 commits)
  move content test into action test to make test finish faster in both studentCourseJoinConfirmationPageUiTest & instructorCourseJoinConfirmationPageUiTest
  minor change of the prototype
  [Fixes #72670696] add content tests for *joinConfirmationUiTest
  adjustment to UI
  Remove missed out references to AnchorPosition.js
  1.specify details for extreme cases 2.add two links test
  editInstr style change
  done with accessControl prototype
  Fix javascript for scrolling
  [Fixes #72606556] another dummy commit
  [fixes #72606556] A dummy commit to check Pivotal integration
  fix previously missed indentation typo
  modify indentation for studentFeedbackQuestionSubmitPageUiTest.java
  a more complete js for accessControl page
  1.delete non-existent css reference in both studentCourseJoinConfirmation.jsp & instructorCourseJoinConfirmation.jsp 2.remove wrong padding style for Confirm and Cancel buttons in instructorCourseJoinConfirmation.jsp
  instructorFeedbackEdit: typo --> Responsesvisible
  Remove AnchorPosition.js
  define ids and fix a js bug
  redo code formatting
  remove unused package
  ...
make ui test green for new comment entity
[Fixes #72669836] Update Comment entity to support multiple recipients
[Fixes #72723036] Provide data migrator to support updated Comment entity
[Fixes #72723036] Provide data migrator to support updated Comment entity

Merge branch '72723036' into Feature-OmniComment
Merge branch 'Feature-OmniComment' into 72669836
update json for new comment entity
[Fixes #72669836] update all related json for new Comment entity

Merge branch '72669836' into Feature-OmniComment
complete PermissionAttributes

test not done yet
commit before adjustment of structure
some const params defined