Implemented five new operations for dynamical semigroups

src/doc/en/reference/dynamics/index.rst

@@ -29,6 +29,7 @@ Arithmetic Dynamical Systems
    sage/dynamics/arithmetic_dynamics/product_projective_ds
    sage/dynamics/arithmetic_dynamics/wehlerK3
    sage/dynamics/arithmetic_dynamics/berkovich_ds
+   sage/dynamics/arithmetic_dynamics/dynamical_semigroup
 
 
 .. SEEALSO::

src/sage/dynamics/arithmetic_dynamics/all.py

@@ -5,5 +5,8 @@
 from .projective_ds import DynamicalSystem_projective
 from .product_projective_ds import DynamicalSystem_product_projective
 from .berkovich_ds import DynamicalSystem_Berkovich
+from .dynamical_semigroup import DynamicalSemigroup
+from .dynamical_semigroup import DynamicalSemigroup_affine
+from .dynamical_semigroup import DynamicalSemigroup_projective
 lazy_import('sage.dynamics.arithmetic_dynamics.wehlerK3', 'WehlerK3Surface')
 lazy_import('sage.dynamics.arithmetic_dynamics.wehlerK3', 'random_WehlerK3Surface')