Jobs may need to run just once

[gemblerz]

The science rules are designed to support recurring executions of application. In some cases, applications in a job need to run just once and "completes," I think most of them would be for testing purposes.

We can think of 2 cases: do this at either plugin level or job level. For example,

scienceRules:
- schedule("myprogram", once=True): True

The once=True can let the scheduler not to schedule "myprogram" once it ran and completes. However, the scheduler may "forget" the fact that it ran the program because it may have limited memory.

In the second case,

successCriteria:
- Once("myprogram")

The Once in the success criteria will let the scheduler know that it can drop the job after a completion of myprogram. However, it is unsure how we can apply this for multiple plugins in a job. If plugins run at different times, the scheduler still has the problem of memorizing.