Add some standard time sources, and remove the miscellaneous trait

Preserve backwards compatibility for old job api.
Provide acceptable defaults for the new execution api.

This closes #238.
Fixes formatting in LoadExecution.
Adds counter to keep track of how many rows were filtered.

This is important to calculate the failure rate, since it is not
sufficient to calculate the failure rate based on the read count.
Adds some more comments for Filter and Validator.