"type" field on host replaced with foreign key "machine_type_id"

JIRA INFRA-281

The network range defines the IP to be allocated.
This is to reserve some specific addresses (for gateway for example).

An admin user should be able to define an interface outside the network
range.

The IP address select field was replaced with a string field
(initialized to the first available IP).

Fixes INFRA-200

Fixes INFRA-197

The interface name shall start with the hostname of the host it is
associated to.

Note that this is only enforced via the UI (from which most users will interact),
not from the API.

Fixes INFRA-195

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