"gateway" tag removed. It could be re-added if needed to overwrite the
default computed gateway for example.

JIRA INFRA-339

Tags and device_types are used as key in Ansible roles.
They shouldn't contain any spaces to avoid issues.

JIRA INFRA-334

- create many-to-many relationships between the user table and
attributes tables (manufacturer / model / location / status / action)
- add a checkbox as the first column of the attributes table to add or
remove an attribute to the favorites
- add a new page to display the favorite attributes

JIRA INFRA-283

Not everyone at ICS is part of the 'ICS Employees' AD group.
We have to accept 'ICS Consultants' as well.

The CSENTRY_LDAP_GROUPS settings now takes a list of groups instead of
just one.

Remove unused is_member_of_all_groups method.

Fixes INFRA-225

- refactor Network class

- network name should be unique and not nullable
- force all name fields to StringField