study.strats.and.answers: A helper function to find best answers to a strategy
In skranz/StratTourn: Tournament of game theoretic strategies

The function is based on simulation.study in sktools

study.strats.and.answers(strats, answers = NULL, strat.par = NULL,
  answer.par = NULL, strat.answer.par = NULL, game = NULL, delta = 0.9,
  R = 5, extra.strat.par = NULL, extra.answer.par = NULL, ci = 0.9, sim,
  score.fun = "efficiency-2*instability-20*instability^2", game.fun = NULL,
  game.par = NULL, verbose = interactive(), disable.restore.point = TRUE)

`strats`	a named list of strategies to study
`answers`	a named list of answer strategies to study
`strat.par`	either NULL or a list with different parameters of strat that shall be studied. (May not run if strats contains more than one strategy)
`answer.par`	either NULL or a list with different parameters of the answer strategy strat that shall be studied.
`game`	a game object, if NULL then game.fun must be provided
`delta`	a discount factor or a vector of different discount factors that shall be studied
`R`	number of repetions of the simulated matches
`ci`	a number between 0 and 1 describing the confidence niveau of the expected payoffs that will be shown in the plots
`sim`	results from a previous call to study.strat.and.answer. New simulations will just be added.
`score.fun`	a string containing the formula for the score function
`game.fun`	a function that generates a game object, like make.pd.game. If NULL game must be provided
`game.par`	either NULL or a list with values for game parameters that shall be studied (a game parameter is an argument of game.fun)