Simulation metric: Time spent working on Project

[Xilconic]

With #4, the simulation results report the 'lead time' of when the project is done.
It's probably valuable to know how many working days were actually used to complete that project.

Example:
GIVEN 2 projects:

• A with priority weight of 10 and 4 work items
• B with priority weight of 0 and 6 work items
  AND 1 throughput metric valued at 2 work items / day
  THEN the expected times worked on each project is:
• A: 2 workdays (while the 'time till completion' is also 2 workdays)
• B: 3 workdays (while the 'time till completion' is 5 workdays)