Better remote file handling

Situation:

Remote files, such as JPEG images, are always opened in web browser, despite the fact that dedicated image viewers such as EOG are perfectly capable of handing http:// and other downloads.

On encountering a file unsupported by web browser, it prompt the user if they want to view OR save the file. The user has to choose between seeing the file just once and not seeing the file right away but being able to view it later. Moreover, they have to choose one of the options before they even know what the file contains.

This sucks; let's do something about it.