Add support for listing real apps instead of everything in $PATH

[TheLastProject]

This should become the new default, especially on non-Linux

[TheLastProject]

For macOS this was added in fb5cdd8. Linux and Windows still remain

[ata2001]

I started working on adding support for desktop entries on Linux.

Todo:

• Parse desktop files and list apps
• Display localized name of apps
• Handle arguments
• Desktop Actions

[TheLastProject]

For displaying localized names, it'll probably be helpful to check settings['_locale'] that the module gets from Pext. It contains the locale Pext is in, so you don't have to do locale detection yourself.

[TheLastProject]

Superseded by #6.