Tags for undeploy (#734)

```
  --include-tags TEXT             Only include requests with matching tags
                                  (comma-separated).
  --exclude-tags TEXT             Exclude requests with matching tags (comma-
                                  separated).
```

Reviewed-on: #734
Co-authored-by: Thomas E Lackey <telackey@bozemanpass.com>
Co-committed-by: Thomas E Lackey <telackey@bozemanpass.com>

stack_orchestrator/deploy/webapp/util.py

@@ -351,3 +351,15 @@ def generate_hostname_for_app(app):
     else:
         m.update(app.attributes.repository.encode())
     return "%s-%s" % (last_part, m.hexdigest()[0:10])
+
+
+def skip_by_tag(r, include_tags, exclude_tags):
+    for tag in exclude_tags:
+        if tag and r.attributes.tags and tag in r.attributes.tags:
+            return True
+
+    for tag in include_tags:
+        if tag and (not r.attributes.tags or tag not in r.attributes.tags):
+            return True
+
+    return False