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>

scripts/gen_tags.sh

@@ -0,0 +1,10 @@
+#!/bin/sh -eo pipefail
+#Generate MD formatted tags from roles and cluster yaml files
+printf "|%25s |%9s\n" "Tag name" "Used for"
+echo "|--------------------------|---------"
+tags=$(grep -r tags: . | perl -ne '/tags:\s\[?(([\w\-_]+,?\s?)+)/ && printf "%s ", "$1"'|\
+  perl -ne 'print join "\n", split /\s|,/' | sort -u)
+for tag in $tags; do
+  match=$(cat docs/ansible.md | perl -ne "/^\|\s+${tag}\s\|\s+((\S+\s?)+)/ && printf \$1")
+  printf "|%25s |%s\n" "${tag}" " ${match}"
+done