This is the declaration of the SplitFun1to3 class.
This class is an abstract class which describes the common interface
of all 1->3 splitting functions, both for Initial State
and Final State Radiation.
***LOOKHERE*** This class is currently kept empty; however, if you have to implement it, you should proceed similarly to the SplitFun1to2 class.
CLASS
SplitFun1to3: