Speed up Measurement Control on large datasets

Measurement Control could take more than a minute to answer on procedures with very high run volume, and the page sometimes stopped loading altogether before any chart appeared.

• Fixed the page stalling on procedures with hundreds of thousands of measurements. The heaviest query dropped from 106 seconds to 5 seconds, and opening a measurement now answers in well under a second.
• Improved the cold page load so the sidebar filter counts wait for the main chart instead of competing with it, which is what made every query on the page slow down at once.
• Added a clear message asking you to narrow the date range or the filters when a query is too broad, in place of a page that never finished loading.