Parameters used in evolutions

• ahfinder::ahf_findevery (steerable)
  Specifies how often the finder is called. The default is to find horizons at every iteration.
• ahfinder::ahf_findafter (steerable)
  The number of iterations after which the thorn is called the first time can be specified by this parameter. Here the default is 0, calling the thorn also on the initial time slice.
• ahfinder::ahf_findaftertime
  Instead of specifying the number of iterations, one can specify after how much coordinate time the thorn is called the first time. When different from zero, this parameter overrides the value of ahf_findafter. Default here is also 0.