Allow to customize the default selected values:
- the default network prefix can be defined in the configuration (default to 24)
- the default first and last IP chosen can probably be improved
  it defaults to hosts[9] and hosts[-5] if the list has more than 15
  elements or the first and last otherwise

Note that when using a small prefix (< 19), the number of possilbe IPs is quite
large and updating the first and last IP select field takes some time...

Scroll up to ensure the from input is not hidden below the navbar.

See https://github.com/twbs/bootstrap/issues/1768

Rendering done client side using Showdown: http://showdownjs.com
Live preview is shown below the form.
Only raw text is saved in the database (no HTML).

Note that no XSS filtering is done!
See https://github.com/showdownjs/showdown/wiki/Markdown's-XSS-Vulnerability-(and-how-to-mitigate-it)

Markdown to HTML converter in Javascript

Use endpoint argument to avoid collision with flask-admin Network

- disable item field for virtual hosts
- pre-fill interface name with hostname

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

- All created tokens are stored in the database.
  To revoke a token, we just delete it from the database.
  Tokens not found in the database are thus considered unvalid / revoked.

- Add button to copy generated token to the clipboard

- Redesign profile page

See https://clipboardjs.com

Open source icon set with ready-to-use fonts for bootstrap
See https://useiconic.com/open/

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.

- update flask-bootstrap
- update datatables to v1.10.15 for bootstrap 4 support