Rename Users' Name to "Anonymous" on Anonymous Posts in the UI

[J0nathanLai]

To successfully change the posts to indicate anonymity, the changed data fields in the backend should reflect its changes in the frontend and not indicate the users' actually name or ID; it should say "Anonymous" or anything similar in the UI.

Estimated effort for each task: High
Dependencies among tasks: #25
Milestones to indicate which sprint the issue should be completed in (Sprint 1, Sprint 2, Stretch): Sprint 2
Acceptance criteria that describes how you know this task is done: if the UI on NodeBB shows that the post is from an anonymous user after the user clicks the anonymous post button and posts the post.