unfortunate label & icon for mail list "options"

[mbohlender]

A lot of testers failed to find a way to change the ordering because they could not recognize that it hides behind the sliders icon with the meaningless label "options".
We should pick a better label and icon.

The sliders are already used by our roundcube wide settings.
One option might be something like "sort-amount-asc" from fontawesome

"sorting" might be a better label. It is not perfect though.

[alecpl]

I thought it's natural that list footer buttons belong to the list. However, on phones the list is our initial landing page and the Options button might be treated as some general options not list options.

So, a better icon and maybe "List options" label would do the trick. Though I also do not like to "sorting" icon.