Remove extraneous statement

The $scope.filterUsers = '' statement that I'm removing here was in the
wrong place entirely. It should have been at the top of the controller
function (and a different commit has already placed it there).
Improve filter feature in listview

When the listview filter feature was written simply in the form of
"items='someValue | filter:someOtherValue'", everything worked fine when
loading pages normally. But when running E2E tests through Protractor,
errors like "[$rootScope:infdig] 10 $digest() iterations reached." were
showing up. The more complex approach in this commit, where the
directive itself becomes filter-aware, allows it to work both in normal
use cases and also in E2E test scenarios.
Improve setupTestEnvironment.spec.js

Stop using Astrolabe for the site admin page, as it adds a layer of
indirection (and complexity) for no benefit over our simpler approach.
Also end the setup by logging out of the admin user and logging in as a
normal user, since otherwise the first test run after the setup seems to
be failing.

With this commit, the entire test bar is green again for the first time
in several days.