Fix package info for 404 errors & blacklisting pkgbase names
We try to find packages when a user enters a URL like /somepkg or accidentally opens /somepkg.git in the browser.
However, it currently also does this for URL's like /pkgbase/doesnotexist and falsely interprets the "pkgbase" part as a package or pkgbase name. This in combination with a pkgbase that is named "pkgbase" generates some misleading 404 message for URL's like /pkgbase/doesnotexist. (Seems that is constantly happening btw)
Issue report: #498
Let's also add blacklist checking for pkgbase and the name pkgbase
to the list