Classes should be ecotype -> population -> metapopulation with MCMC sampling

[joethorley]

The base class should be an ecotype - which is one schedule with one SR
A population should consist of one or more ecotypes which have different schedules but the same SR
A meta population should consist of one ore more populations which have different SRs

In all cases the fish are indistinguishable by anglers and but experience the same exploitation rate for adults of a certain size.

Uncertainty should be handle by using distributions for the parameters with MCMC sampling.

[joethorley]

this should likely be a new package ypr2

[joethorley]

and weight and name should be properties of ecotypes (as well as populations in a metapopulation)

[joethorley]

Arguable these parameters should be properties of populations not ecotypes

  check_same(x, "BH")
  check_same(x, "Rk")
  check_same(x, "tR")
  check_same(x, "Rmax")
  check_same(x, "pi")
  check_same(x, "Llo")
  check_same(x, "Lup")
  check_same(x, "rho")
  check_same(x, "q")

[joethorley]

related issue of #62