ENH: Add more educational models

[timmens]

PyLCM does not have enough educational models that focus on the Economics. Once we have a running documentation, we should showcase a few example models designed for educational purposes. In this issue we collect some example models for this purpose:

Simple College and Consumption Model

• 18-yo, 3 different periods: 4yrs, 45yrs, 25yrs

  • Within periods, will always do the same?

• Two decisions:

  • Go to college y/n
  • How much to borrow / save

• Environment:

  • If not going to college: Earn some money in period 0, earn amount x_nc in main working life
  • If going to college: Earn nothing in period 0 (even pay some cost?), earn amount x_c in main working life
  • Earn nothing during retirement
  • Can add endowment, borrowing costs / constraints
  • Can add uncertainty over whether going to college leads to x_c or x_nc
  • Can add different expectations about this

• Utility:

  • Function of consumption (CRRA, linear, log)
  • Need to scale with length of periods in suitable way