CheckHistory job should support relative date/time values like -6h

Current Situation

For queries about previous executions of jobs and job chains it is possible to specify absolute values like "12:00:00". In addition it is possible to specify the day relative from the current date like "-1:12:00:00" which translates to "yesterday 12 o'clock".

Example: isCompletedSuccessfulAfter -1:12:00:00

Desired Behavior

It should be possible to specify relative values for the period like "-6h" which translates to "6 hours in the past".

Example: isCompletedSuccessfulAfter -6h