[App Management] Add Permission Page for PWA

This CL adds a permissions page for PWAs. It also cleans up and
rationalizes all the HTML/CSS for App Management.

Bug: 906508
Change-Id: I806f7269958cc83e4f9112d307f679ef0d300e05
Reviewed-on: https://chromium-review.googlesource.com/c/1373931
Reviewed-by: calamity <calamity@chromium.org>
Reviewed-by: Eric Willigers <ericwilligers@chromium.org>
Commit-Queue: Cecilia Ni <ceciliani@google.com>
Cr-Commit-Position: refs/heads/master@{#617418}
13 files changed