Better logging and/or error reporting

[eaburns]

Sometimes the error you get when you fail to add a feed is just useless. We should log errors at a finer level, or report better errors.

[juggler885]

When I get an error, it is a blank page with a text as the error. This requires me to manually go to the url (or hit back) to get back to a page with navigation. If possible, could we have an error page (a page that lists the errors) that has the top right navigation bar?