Expanding named filters in path-based filtering options

[mickael-menu]

Named filters are currently expanded only in the path argument of filtering options, e.g.

[filter]
draft = "--tag 'draft OR todo'"

$ zk list draft --interactive

By expanding it in filtering options taking path arguments as well, we open the possibility for easy nested filtering commands. Named filters would become some kind of "virtual directories".

$ zk list --exclude draft