Add call center baby staffing simulation-optimization model

[chloetsetsekas]

Adds a call center baby staffing simulation-optimization problem to simopt.

Implemented a discrete-event call center simulation model with Poisson arrivals, service times, customer patience times, trunk-line capacity limits, lunch breaks and overtime handling for agents, customer abandonment, and blocked calls.

Created .rts file outlining the context and explaining the optimization problem.

Features:

• CallCenterMinCost optimization problem
• CallCenter model wrapper
• Staffing decisions using a 17 x 4 staffing matrix: 17 possible shift start times and 4 possible lunch-break timings
• Helper function for generating demand-based staffing plans to get an alternative "better" starting solution
• Helper function for plotting staffing levels versus demand

Notes:

• The model currently returns simulation-based performance estimates and staffing cost
• Optimal solutions/objective values are not yet known