New get_json method on test client response.
See http://flask.pocoo.org/docs/1.0/testing/#testing-json-apis

- requirements-to-freeze.txt is used to list only the needed packages
- requirements.txt is used to build a reproducible environment
- requirements-dev.txt is for testing and building the documentation

The official flask-bootstrap is still not compatible with bootstrap 4.
The application basically only uses the main template and one macro.
It's easier to include directly bootstrap in CSEntry.
It makes upgrading to the latest bootstrap much easier and removes a
dependency.

Update to bootstrap 4.1.3

Added:
- jquery-3.3.1.min.js
- bootstrap.bundle.min.js (include popper but not jquery)

Note that jquery.slim can't be used.
We need for example $.getJSON for datatables.

JIRA INFRA-424

JIRA INFRA-414

This is not super clean. The model and device_type belong to the host.
This is for easy access from the API.
But it would be better to have a "expand=true" query parameter and return the
host as a dict.

JIRA INFRA-414

JIRA INFRA-414

JIRA INFRA-412

- add ansible_groups_hosts_table for many-to-many relationship between
groups and hosts
- add new api endpoint /network/groups

JIRA INFRA-412

Allow to enter Ansible variables on host in YAML format.
Use codemirror (http://codemirror.net) to make editing YAML easier.

JIRA INFRA-412

+ yaml mode

Use the before_flush hook to trigger the core services update.
It's much nicer than having to call a method in several places.

The core services update is triggered on creation/modification/deletion
of an Interface.

In the before_flush we can manipulate the session (add objects) but we
shouldn't call commit.
The db.session.commit() was removed from the launch_task method.

- black
- flake8

See https://pre-commit.com

https://black.readthedocs.io/en/stable/

Add new jinja2 filter to format datetime

torn was configured to run playbooks on the GPN via a proxy.

- the version of libiconv used was removed...
- fix formatting

Avoid calling the database several times.
Several attributes can be updated in one call.

Only save exceptions that occur before the AWX job was triggered.
If the AWX job failed, we can refer to the logs on AWX.

Allow to display tasks

JIRA INFRA-403