Implement the store.AddBundle method

Also implement a cstomized CharmURL type so that we can easily deal with partial URLS.

Updated dependencies so that we are now using the updated names/charm.v2 packages.

I think we should de-duplicate here by using a map.

something like:

 	urls := make(map[string] *params.CharmURL)
 	for _, _, service := range data.Services {
    		url, err := params.ParseURL(service.Charm)
    		if err != nil {
    			return nil, err
 		}
 		urls[url.String()] = url
 	}
        // convert to slice
 	return urls, nil