Fix tests after merging ES module based app shell.

[shaper]

Preparing to land the es6-modulify branch. Known items to resolve subsequently:

• gift shopping demo flow selenium test is broken (actual test seems to duplicate the final clause in the description text incorrectly, perhaps a template issue)
• arc-app.html not yet converted, thus app-shell.html still remains as well. Possible cdn path construction issue to resolve.
• unit tests for persistent-arc.html, dancing-dots.html, and good-map.html are disabled as they need to import the involved code which now lives in ES modules. Fixing may require emulating what arcs does via sigh test to generate and run mocha tests in a manner as touched upon in Support ES6 style tests without transpiler usage mochajs/mocha#3006

FYI @sjmiles

[sjmiles]

• localize dependencies instead of list in AppShell.js
• remove window globals for ArcsUtils and Xen*

[shaper]

Only one item remains: "...unit tests for persistent-arc.html, dancing-dots.html, and good-map.html..."

[smalls]

Now tracked by PolymerLabs/arcs#713.