xci: Add main playbooks and files

This patch adds the main/common playbooks, files, and templates to
be used for all flavors.

The provisioning and OpenStack installation process will be as below
- provision VMs for flavor using bifrost
- once the VMs are provisioned, configure-localhost.yml playbook will
be run, preparing the localhost in order to ensure the right playbooks
(configure-opnfvhost.yml and configure-targethosts.yml), inventory files
and var files are in place before we proceed with configuring opnfv host.
- after getting the right files for the flavor, opnfv host will be
configured using configure-opnfvhost.yml playbook.
- finally, the target hosts will be configured.
- once the above process is completed, openstack-ansible playbooks will
be run, setting up hosts, infrastructure and OpenStack.

Change-Id: I6e08b2cfdab9627f765e6fc414917b09f953cab2
Signed-off-by: Fatih Degirmenci <fatih.degirmenci@ericsson.com>