Move most IDR config to this repo

[manics]

Moves most of the IDR configuration into this public repo.
Adds placeholders for variables which should remain secret, where possible a public default is given:

$ git grep idr_secret
idr-playbooks/files/IDR-OMERO-52-omero.j2:config set omero.web.public.password {{ idr_secret_omero_web_public_password | default("") }}
idr-playbooks/group_vars/omero-hosts.yml:omero_system_uid: "{{ idr_secret_omero_system_uid | default(546) }}"
idr-playbooks/group_vars/omero-hosts.yml:omero_logmonitor_slack_token: "{{ idr_secret_omero_logmonitor_slack_token | default(None) }}"

Most of these playbooks should therefore run without any private configuration.
Note: work on changing omero_system_uid in the IDR is ongoing.

Testing

Ansible group_vars can be in two locations, the playbook directory and the inventory directory, with the former taking precedence. This means when you run a playbook in idr-playbooks idr-playbooks/group_vars is automatically included, and if you also specify an inventory (ansible-playbook -i INVENTORY/PATH) INVENTORY/PATH/group_vars will be included.

I've only tested this on top of #124

[manics]

What would be ideal is if we could automatically create a public user if it doesn't already exist, but that probably requires a custom omero ansible module.

[joshmoore]

Merging for the upcoming testing via demo3 deployment.