Code review comment for lp://qastaging/~sil/desktopcouch/viewparams-497143

Allow execute_view to take a dict of additional parameters, such as { "descending": True }, which can be passed on to the underlying view, thus allowing extra params to be passed onto the CouchDB request. See https://answers.edge.launchpad.net/desktopcouch/+question/93862 for a user request for this.