Before, the information needed to display different parts of the UI was
tightly coupled to the specific messages being sent back and forth to
the backend worker. Separating out a models package allows us to be more
specific about exactly what a backend is able to and required to provide
for the UI.

Before, the information needed to display different parts of the UI was
tightly coupled to the specific messages being sent back and forth to
the backend worker. Separating out a models package allows us to be more
specific about exactly what a backend is able to and required to
provide for the UI.

Assuming we always have a sorted dirlist
(other code depends on that already), we don't need to loop over the
dirStore.
Any filtering done should be performed elsewhere

Also sets the public List() method to return the unfiltered
list of directories directly from the store.

Credit for this fix goes to Reto; I guess if we're not gonna be mutt
we should probabaly do things correctly.

Now that this is available in the upstream, we no longer need to
maintain a parallel implementation.

This reverts commit 0e55637aac92e748267559b7aa91a188a17c386f.

This fixes prev/next-folder that broke after
546dfcd76dd228e0605359e9985f0b6a5672e8fa