Kill time includes prerequisites

[sylvainhalle]

When an experiment has to generate prerequisites before running, its execution time includes that process. This means that an experiment may get killed by the assistant while it is still generating the prerequisites.

An experiment should have two "start" times: the start of the whole process, and the start of the run method. Timeout should apply to the second, not the first.

[sylvainhalle]

In a nutshell:

• Add a new status RUNNING_PREREQ when the experiment is generating its prerequisites
• Split the m_maxDuration field into max duration for prerequisites and execution
• Split the getRunningTime() method in the same way
• Adjust the LinearAssistant to timeout experiments according to prerequisites or running max durations