Improvements to the gPodder command-line interface

For quite some time now, gPodder ships with the "gpo" utility - a command-line utility to carry out some basic tasks (subscribe, update, download, ...) with the gPodder database. For the future version, we have some cool new features that I'd like to share with you today (you can try them out in the "tres" branch of our Git repository):

• Interactive mode (just run "gpo", and you get a "gpo>" prompt), complete with readline support and tab completion :)
  
• Automatic paging of long episode lists ("less"-like scrolling, powered by pydoc)
• Handling of keyboard interrupts in interactive mode

Of course, the feature set of "gpo" does not cover all that's possible right now with the GUI, but it would be easy to extend if someone wants to step up and contribute some features. The latest version, 2.13, already contains some improvements to the CLI, and you already get nice, colored terminal output when updating feeds or downloading episodes.