Configurable auto-create for different entity types and meta tags

I was following http://drupal.org/node/1088344 which appears to be closed. I too need the feature of adding meta tag fields to vocabularies. Since I don't see this has been done yet (you mentioned you are working on it in March), I am attaching a patch as a start.

The patch does the following:
* Auto-creates the meta tag fields for all found vocabularies, in the same way as it does for content types.
* Changed the labels for the fields to better state their purpose. For e.g. in Vocabularies, there is already a 'Description' field. So adding another one is confusing.

Please review.