Add tags

Add tags to allow more granular tasks filtering.
Add generator script for MD formatted tags found.
Add docs for tags how-to.

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

roles/network_plugin/flannel/meta/main.yml

@@ -2,3 +2,4 @@
 dependencies:
   - role: download
     file: "{{ downloads.flannel }}"
+    tags: download

roles/network_plugin/flannel/tasks/main.yml

@@ -26,6 +26,7 @@
 
 - set_fact:
     flannel_subnet: "{{ flannel_subnet_output.stdout }}"
+  tags: facts
 
 - name: Flannel | Get flannel_mtu from subnet.env
   shell: cat /run/flannel/subnet.env | awk -F'=' '$1 == "FLANNEL_MTU" {print $2}'
@@ -34,17 +35,21 @@
 
 - set_fact:
     flannel_mtu: "{{ flannel_mtu_output.stdout }}"
+  tags: facts
 
 - set_fact:
     docker_options_file: >-
       {%- if ansible_os_family == "Debian" -%}/etc/default/docker{%- elif ansible_os_family == "RedHat" -%}/etc/sysconfig/docker{%- endif -%}
+  tags: facts
 
 - set_fact:
     docker_options_name: >-
       {%- if ansible_os_family == "Debian" -%}DOCKER_OPTS{%- elif ansible_os_family == "RedHat" -%}other_args{%- endif -%}
+  tags: facts
 
 - set_fact:
     docker_network_options: '"--bip={{ flannel_subnet }} --mtu={{ flannel_mtu }}"'
+  tags: facts
 
 - name: Flannel | Remove non-systemd docker daemon network options that don't match desired line
   lineinfile:
@@ -73,4 +78,4 @@
     - restart docker
   when: ansible_service_mgr == "systemd"
 
-- meta: flush_handlers
+- meta: flush_handlers