Allowing metrics store to perform queries either missing types OR missin...

...g groups (the store will query the best index in both situations). One of these MUST still be supplied, however.
All of the branching logic in this class method is a little crazy.

For example if group = null and name = null, then the branching logic gets to this point and cqRegex = null.  This means there is no point in using a regex filter.