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/kubernetes/master/tasks/pre-upgrade.yml

@@ -3,17 +3,20 @@
   stat:
     path: /etc/systemd/system/kube-apiserver.service
   register: kube_apiserver_service_file
+  tags: [facts, kube-apiserver]
 
 - name: "Pre-upgrade | check for kube-apiserver init script"
   stat:
     path: /etc/init.d/kube-apiserver
   register: kube_apiserver_init_script
+  tags: [facts, kube-apiserver]
 
 - name: "Pre-upgrade | stop kube-apiserver if service defined"
   service:
     name: kube-apiserver
     state: stopped
   when: (kube_apiserver_service_file.stat.exists|default(False) or kube_apiserver_init_script.stat.exists|default(False))
+  tags: kube-apiserver
 
 - name: "Pre-upgrade | remove kube-apiserver service definition"
   file:
@@ -23,3 +26,4 @@
   with_items:
     - /etc/systemd/system/kube-apiserver.service
     - /etc/init.d/kube-apiserver
+  tags: kube-apiserver