Add some functions/constantes in string module
enable module constant as default value in a function
We can use ImportIds pass on a list
Fix context for functionanalysis
Fix assign and augassign management in ImportesIds
Correctly manage variable used before assignement in a If statement in a Loop
conversion from string have to be explicit to avoid conflict
Add constant evaluation time out in the TODO list
Add functions in string module

* strip, lstrip and rstrip
Handle second parameter in enumerate intrinsic

* second parameter is the first number returned (default is 0)
Add combinations in itertools

* combinations return all the possible combination of n elements in an iterable
example: [i for i in itertools.combination("ABC", 2)]
    -> [("A", "B"), ("A", "C"), ("B", "C")]

* it is a forward iterator as output order matter