refactor speedtests handling, ensure rewards only include tests up until epoch end

[andymck]

Refactor the speedtests to prevent scenario whereby the rewards can use reports from after the epoch end. To accommodate this I had to explode the speedtests reports in the DB from 1 row containing an array of up to 6 reports out into 1 row per report.

At the same time i have split the averaging code out from the speedtest module into its own module for better readability and maintainability.

• Add migration to explode speedtests out to 1 test per db row
• delete speedtests after rewarding ( ensure we keep 48hrs worth of tests )
• handle todo's
• test locally
• tidy up
• add indexes to speedtest table