- RQ Dashboard shall only be accessible to admin users
- "REDIS_URL" is hard-coded in rq-dashboard (had to rename RQ_REDIS_URL)

Add a last modified query parameter to static resource.
This will force the browser to re-load resources (css, js...) after a new deploy.

- Main blueprint used to declare custom views for all blueprints.
(keep inventory blueprint cleaner)
- Add url_prefix to each blueprint

main blueprint splitted in:
- inventory
- networks

Use the session instead of URL parameters to store the last network
chosen.

- refactor Network class

Catch exception when no network exists (null is passed as network_id).

This can be done via the Admin interface but this latter shall be
restricted to admin users. This simple page allows the group "create"
to easily add new Manufacturer, Model or Location.

Most items won't have a name.
hostname could be added in a separate table if required.