Version 1.2.3: Performance improvements + misc

Improved redraw algorithm to not repaint unneeded parts of the screen. Reduces CPU usage significantly on some machines. Other miscellaneous improvements also documented below.

Changelog

1. Increased redraw interval from 100ms to 1s unless a realtime UI component (downloads, player) is visible
2. Fix some code branches failing to sleep their thread, resulting in high CPU usage
3. Improve/add some messages for queue reloading and episode enqueueing
4. Fix table scrolling. There is still a known issue when jumping with more than one element at a time
5. Add message for empty queue instead of just a blank UI
6. Fix height bound checking for components, hence eliminating overdraw and gaining some performance
7. Add vim-like jump bindings using "g" and "G"
8. Make long menu text get clipped from the end backward rather than from the start forward. This makes it easier to spot the difference between similar episode names ("S01-E01 - Whateverpodcastname" will show the last part of the name instead of the repetetive parts)
9. Create the downloads directory if it does not exist instead of throwing an error and exiting
10. Minor performance improvement to download startup
11. Improve error message for invalid media files