Reduce query count required for cron-based samples

[codeactual]

Currently samples created via Cron/Tool/runSamplers.php require 6+ queries to update `scalars` with lock states and new value, and insert the new row into the correct sample table.

[codeactual]

Partial work completed in 27f4077.

[codeactual]

Update createSample() to accept a $value array.