Replace new lines with <br>s;
Add uuid to created comment's list item;
Disable new_comment_ok/cancel right after click
Completed flow of POST request for creating a SheetItemComment
Added some spinner goodness to comment creation;
Replaced disabling of new_comment buttons with just sleeping them after click
Invalidate cache of current sheet after adding a comment;
Bump number of comments in discussion in the item's comments icon;
Add the created comment to the discussion of the item in current LatestSheet collection
Initial implementation of download sheet drop menu button