remove spinner later or insert views earlier

[thvitt]

on slow devices (like Wuerzburg’s CIP pool zero-client solution) there might be a considerable delay between removal of the spinner and display of the actual views’ contents in the document viewer. This may lead to the impression that there is something broken, especially since the browser’s load feedback already shows “finished”.

One solution might be to remove the spinner only after all views have finally loaded, which would involve making all views’ setPage() return proper promises that don’t resolve until the contents is on screen.