Use outer join to add quality metrics data instead of loop

[mjstealey]

Currently the quality metrics data is queried separately and added to the CMAQ values data by doing a utc_date_time comparison in a loop.

This is inefficient and should be done as an outer join to the CMAQ value query itself.

Per discussion with @hyi regarding experience with @arunacs at hackathon. Existing implementation is too slow for queries at year long range.