Allow to specify minimum time period between testing in the manifest

[filip26]

Hi,
this is a nice to have functionality that would allow setting a minimum time period between a test suite run against an API. All implemeters could benefit out of it as some don't mind having an API tested frequently but the others rather prefer longer periods of time.

[aljones15]

This actually is not that hard to do, you would need to list the frequency per month you want the runner to run against you and then calculate the week of the month the run is occurring on and then not test your implementation that week. This would result in your implementation not being in the report some weeks though so this feature does require some thought.