Add Py35 compatible type hints

[PythonCoderAS]

Fixes # (provide issue number of applicable)

Parent PR: #1164

Combines:

• Add inline types to const.py and endpoints.py #1169
• Add inline types to config.py #1170
• Add inline types to exceptions.py #1171

This PR adds type hints and makes them compatible for Python 3.5, which supports type hinting in functions only.

Py 3.5 compatible:

def test_function(arg1: str, arg2: str) -> Dict[str, str]:
    return {arg1: arg2}

Py 3.6+ compatible:

class Test:
    classDict: Dict[str, str]
    def test_function(self, arg1: str, arg2: str) -> None:
        self.classDict = {**self.classDict, **{arg1: arg2}}

[bboe]

Thanks!