aw_get_calculatedmetrics() - return comma-separated set of tags if tags is used in expansion

[gilliganondata]

The tags argument for expansion in aw_get_calculatedmetrics() appears to return a list object in the tags column. Since many calculated metrics will have no tags or only a single tag, returning a commas-separated string with the tags seems like it would be cleaner to use, since this would, presumably, be returned primarily so that a subsequent call that uses tagnames would then be executed.