Followup to b53449eac9,
it was too easy to add broken routes which would break
configuration for the whole site, so now we validate ember
routes on save.
NOTE: Most of this is experimental and will be removed at a later
time, which is why things like translations have not been added.
The new /admin-revamp UI uses a sidebar for admin nav. This initial
step adds a script to generate a map of all the current admin nav
into a format the sidebar to read. Then, people can experiment
with different changes to this structure.
The structure can then be edited from `/admin-revamp/config/sidebar-experiment`,
and it is saved to local storage so people can visually experiment with different ways
of showing the admin sidebar links.
