Power operator is_kind_of does not work on positive integers

the power operator seems to think that an integer to the power of another (positive) integer is not a kind of integer.
This leads to an error when doing something like the following:
```
from docplex.cp.model import *
mdl = CpoModel()
x = integer_var_list(3, 1, 10, "X")
mdl.add(( x[0] ** x[1]) // x[2])
```

Because the division only accepts integer expressions