Updating comment page to be similar to Notification Comment page

Current CommentViewController completely removed and a new one created from scratch. It might be easier to look at the whole class during the review.

isLiked and likeCount properties added and stored. /cc @astralbodies 

Closes #2317 and fixes #1656. A separate issue created to implement the header using the post details: #2528.

@jleandroperez Can I bother you with a review?
Incoming annoying comment: Can we turn this into a constant?