New Query Options tray added

For scope, see: https://issues.apache.org/jira/browse/COUCHDB-2347

Two important things to mention:
1. The "Compact View" button has been removed. I want to discuss with @seanbarclay about whether it should really appear in the tray.
2. There's an outstanding issue (outside this ticket) where the header bar doesn't always show the correct content when navigating from page to page.
I believe docs you're referenced is http://docs.couchdb.org/en/latest/couchapp/views/intro.html?highlight=group_level#the-view-to-get-comments-for-posts (and a bit below)?

Not sure, but group_level=exact is a legacy thing that isn't actual any more (btw. nice found!). It origins to https://github.com/apache/couchdb-couch-mrview/blob/master/src/couch_mrview_http.erl#L397 and as you see `group=true` is actually sets special value `exact` for `group_level` field but in the same time parser requires `group_level` query parameter to have integer value.