Update repo README, add compatibility check, sample config files

In this commit:
  - Add execution environment, required additional packages,
    supported software releases, and links to Ansible installation
    as well as StarlingX deployment guides to repo README.rst
  - Add check for supported host software versions to bootstrap playbook
  - Add example files for a sample setup of 2 hosts, a site.yml and a
    secret file which the users can copy to the location of their
    choice and customize to suit their remote bootstrap requirements.

Story: 2004695
Task: 34753
Change-Id: I400021a5a460e1686ef717632c70123b2a93064a
Signed-off-by: Tee Ngo <tee.ngo@windriver.com>

examples/remote/hostname1.yml

@@ -0,0 +1,3 @@
+timezone: Japan
+cluster_host_subnet: 192.168.207.0/24
+external_oam_floating_address: 172.16.0.17

examples/remote/hostname2.yml

@@ -0,0 +1,3 @@
+system_mode: duplex
+management_subnet: 192.168.204.0/24
+external_oam_floating_address: 172.16.0.144

examples/remote/hosts

@@ -0,0 +1,15 @@
+---
+all:
+  hosts:
+    hostname1:
+      # Ansible host IP is the IP of the controller host that is externally
+      # accessible for controller bootstrap and system deployment purposes.
+      # This IP can be created via DHCP or statically.
+      ansible_host: 172.16.0.17
+    hostname2:
+      ansible_host: 172.16.0.144
+
+  vars:
+    ansible_ssh_user: sysadmin
+    ansible_ssh_pass: St8rlingX*
+    ansible_become_pass: St8rlingX*

examples/remote/sample_secrets.yml

@@ -0,0 +1,24 @@
+# The following are configuration parameters that should be stored
+# in secrets files using Ansible vault.
+#
+# Bootstrap specific parameters stored in the vault must have vault_
+# prefix. The same rule is not applied to Ansible specific parameters.
+#
+
+# The following settings could be host specific, in which case they
+# can be placed in the <inventory_hostname>_secrets.yml where
+# applicable.
+vault_admin_username: stx-admin
+vault_admin_password: Boot5trap*
+
+# The following settings are usually common to all hosts, in which
+# case they can be placed in the secrets.yml file.
+vault_password_change_responses:
+  yes/no: 'yes'
+  sysadmin*: 'sysadmin'
+  \(current\) UNIX password: 'sysadmin'
+  (?i)New password: 'Boot5trap*'
+  (?i)Retype new password: 'Boot5trap*'
+
+ansible_become_pass: Boot5trap*
+ansible_ssh_pass: Boot5trap*

examples/remote/site.yml

@@ -0,0 +1,7 @@
+# Configuration parameters in this file will apply to all
+# hosts in the hosts file unless they are overwritten in the
+# inventory_hostname.yml file or at the command line.
+external_oam_subnet: 172.16.0.0/12
+external_oam_gateway_address: 172.16.0.1
+dns_servers:
+  - 1.1.1.1