We have agreed to remove support for Oracle Linux.

http://lists.openstack.org/pipermail/openstack-discuss/2019-June/006896.html

Change-Id: If11b4ff37af936a0cfd34443e8babb952307882b

Instead of changing Docker daemon command line let's change config
for Docker instead. In /etc/docker/daemon.json file as it should be.

Custom Docker options can be set with 'docker_custom_config' variable.

Old 'docker_custom_option' is still present but should be avoided.

Co-Authored-By: Radosław Piliszek <radoslaw.piliszek@gmail.com>
Change-Id: I1215e04ec15b01c0b43bac8c0e81293f6724f278

Change-Id: Icf3f01516185afb7b9f642407b06a0204c36ecbe
Closes-Bug: #1840315
Signed-off-by: Radosław Piliszek <radoslaw.piliszek@gmail.com>

Docker is now always installed using the community edition (CE)
packages.

Change-Id: I8c3fe44fd9d2da99b5bb1c0ec3472d7e1b5fb295

This ensures we have version-specific references to other projects [1].
Note that this doesn't mean the URLs are actually valid - we need to do
more work (linkcheck?) here, but it's an improvement nonetheless.

[1] https://docs.openstack.org/openstackdocstheme/latest/#external-link-helper

Change-Id: I118e4d211617c5df66ff04dc04e308a1d2fc67ad

Change-Id: I89d9f7a90d72e6c5df7dde078ed7407eedd6f92f

Change-Id: I3bd50cb1e7db85acbf8ab20fc7bdd945b5232aaa

Change index to ease identify what service want to look.
Split docs into more specific folder such as networking
and storage.

Change-Id: Ic7ac12b3dd555fa5c018eeb897ccd4a5a2dfe8f3