Loosen version pinning for Django ...

This change is in accordance with https://github.com/digitalocean/netbox/issues/2808

Update Alpine ...

This updates to the newest stable version (Alpine 3.9)

Update Alpine ...

This updates to the newest stable version (Alpine 3.8)

✨ Don't lock Django to explicit version ...

... but rather use the same definition that is currently used in
Netbox's `requirements.txt`.

♻️ Make netbox-worker it's own container ...

One container should ideally have one responsibility [1]. Therefore I
implemented the netbox-worker to start in it's own container. This is
possible, because netbox and the worker communicate via redis anyway.

They still use the same image underneath, just the "command" they
execute while starting different.

Or in other words: I see no reason to introduce supervisord, when we
already have docker-compose which can take care of running multiple
processes.

Also, here's another benefit: Now it's possible to view the logs of the
webhook worker independently of the other netbox logs (and vice-versa).

Other changes in this commit:
* I don't see a reason to put a password for Redis in the docker-compose
  setup, so I removed it.
* Slightly changed the nginx config, so that the nginx startup command
  becomes simpler and any error should be visible in the docker log.
* Some housekeeping in the `Dockerfile`.
* Added some troubleshooting advice regarding webhooks to the README.

I'd like to thank Brady (@bdlamprecht [2]) here who did the harder
work of figuring out what's even required to have webhooks working. [3]

[1] 
https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#decouple-applications
[2] https://github.com/bdlamprecht
[3] https://github.com/ninech/netbox-docker/pull/90

Working implementation of webhooks using new 'redis' container

Update to Alpine 3.7 ...

Because the tag "python:3.6-alpine" points to Alpine 3.4 which is now
end of life (as of 2018-05-01) the image now pulls the Alpine 3.7 python
image

Move config to /etc/netbox/config (Fixes #54) ...

With this the configuration is moved to /etc/netbox/config and the
default reports directory is set to /etc/netbox/reports. This enables
the user to mount reports from a config map or persistent volume in
OpenShift.

✨ Introduces a Netbox Docker project version

Adding in support for NAPALM

Externalize gunicorn-config ...

This moves the gunicorn_config.py into /etc/netbox so that it can be
easily mapped through a Openshift config map

Modifications for Openshift ...

With these modifications the netbox containers can run on Openshift.
The configuration files can be imported from a config map to the
'/etc/netbox' directory and will be loaded from there.

🐞 Be More Explicit On Paths

✨ Include Initializers ...

Initializers are startup scripts for common tasks like creating custom
fields. These are problems many users of Netbox Docker potentially face
and are therefore worth sharing.

❇️ Adds new options to the build script

Added ttf-ubuntu-font-family ...

The present build does not include a font-family causing Graphviz to render text as blank squares, including the ttf  ubuntu font-family means text is rendered correctly

🐞 The upstream repo remove the docker config ...

.. so I copied it over to this repo.

Removes workaround for Django Rest Framework

Add description for library

Set right version of django rest framework

🐳 Adds the possibility to overwrite the CMD

🐳 Change to the actual workdir

🔼 Introduces a more recent gunicorn

🐳 By default, build `latest` from the `master` branch

Updates default Docker build branch to a stable version

Fixes logging config that prevented gunicon launch

Switch to python 3

Merge remote-tracking branch 'chrigl/fix-add-nginx-conf'

Added nginx.conf netbox image ...

Without it, the nginx container of the docker-compose.yml refuses to
start.

Updated for v2.0-beta3