Goal.comment threads

offset is now the commentGuid midlist that is the starting point of the comments returned include-offset now states whether the offset comment should be included in the list token is now the paging token

Descending = true is the default for querying comments because we load the most recent and then the comment guids descend into the past. When we page, we go further into the past.

When Descending = false, we page into the future. The comment guids ascend.

** Note: I decided to force the client to specify descending and ascending, rather than reverse it when an offset was provided. This will require a small change on front.