Ephemeral constants for ANN and inconsistencies in documentation

[CoolRunning]

The docs say that the dcgpy.expression_ann can take ephemeral constants, however the python constructor does not allow it.

https://darioizzo.github.io/dcgp/docs/python/expression_ann.html

Some of the example code does not work, for example

>>> from dcgpy import *
>>> dcgp = expression_double(1,1,1,10,11,2,kernel_set(["sum","diff","mul","div"])(), 0u, 32u)
>>> print(dcgp)

does not work (there is no "expression_double" anymore).

There are inconsistencies in the signatures of some functions, e.g.:

Symbolic regression wants to have columns

https://darioizzo.github.io/dcgp/docs/python/symbolic_regression.html

dCGP-expressions want to have cols

https://darioizzo.github.io/dcgp/docs/python/expression.html