Copied the elements and scripts from the current checkout of the project-config

https://git.openstack.org/cgit/openstack-infra/project-config-example/tree/README.md#n41

Just set random update time
The cloud credentials are expected from the ci nodes' common.yaml via os-client-config

The target is now part of the linters environment, so can be
removed.

Change-Id: I825560b0d83541c0ca1a970f5f9ae9e6a4aeff71
Depends-On: If398a3e0415b2a0ab7f05ce390c18d9b28a85927

Change-Id: I037323c17efd736ff59591200bcffeebd5450cdf

Follow change I2afa7931bf3e18798b95a8af33ccf5ef761c4ad5 on
project-config and introduce a new linters target that is used
for linting on the repo.

Change-Id: I1f81b8ab1fe18a172804b795e40428034fddd803

Manual installation of some basic packages is needed for tox -e zuul,
otherwise you'll get the following errors:

unable to execute 'x86_64-linux-gnu-gcc': No such file or directory
netifaces.c:1:20: fatal error: Python.h: No such file or directory

Change-Id: If112637e70db88dcf91b30f0d564f180633f92bf

`PUBLISH_HOST` does not exist. Correct the documentation to
`your-log-server`

Change-Id: Ie8c20c2bf50b2d5f5a67591462c035cabb1de5be

project-config-compare-xml needs tools/run-compare-clonemap.yaml. Add it from
https://git.openstack.org/cgit/openstack-infra/project-config/tree/tools/run-compare-clonemap.yaml

Change-Id: I049dfd38dce6c66b903ca899247436ba1c440d1b

General doc improvements.
Include the sources for this repo.
Add basic syntax check instructions to use 'tox'.

These were copied from the upstream checks:
https://git.openstack.org/cgit/openstack-infra/project-config/tree/

layout-checks.py was modified to skip check_merge_template()

Depends on nodepool https://review.openstack.org/#/c/189762/