Add option to make Decline non-global

After I review code, there may be enough issues to change that I won't approve the PR but (in the current implementation) I also don't want to decline the PR since the rest of the team then loses visibility. It'd be nice for each reviewer to be able to make the PR as declined without having that completely close the PR. As is, if the PR is left opened, it stays in my Inbox, requiring me to remember if I need to review that PR or not every time I open up Stash to do code reviews.

Alternatively, adding another state to a PR, "Reviewed" would solve part of this problem. (And add another tab to the Inbox to show Reviewed). Any change to the PR could clear the Reviewed flag or the Author could have a button to mark changes as complete.