MinimumSamplingInterval is from Type Duration/Double so a float. Correct xmlparser.

prevents unsupported identity tokens to create a session

* Previously a client could not read values with bad status.
* This functionality can be toggled on and off.
* Added tests.

Fixes #856

get_origin, get_args already defined

- mirror change from mypy
- ignore mypy errors
  - better to fix issues step by step

UAExpert sends its application certificate as client certificate in the initial `CreateSessionRequest`.
The user certificate is sent as `ua.X509IdentityToken` in the request body and has to be looked up there.

* init

* add: is_abstract check and typehints

* change import for Node

* change import for Node

* remove nodeclass-typehints due to import error

* add test for instantiate abstract type

* edit: change ValueError to UaError

* edit: test

support for union types in struct104

Fixed parameter named from lowercase to CameCase in statemachine.install.

use the correct field serializer for the Encoding field by looking up field type instead of hardcoded 'Byte'

__bytes__ on the Buffer object is sometimes returning a bytearray instead of bytes.

Traceback (most recent call last):
  File "C:\Users\ddeason\PycharmProjects\opcua_test\venv\lib\site-packages\asyncua\client\ua_client.py", line 88, in _process_received_data
    data = bytes(buf)
TypeError: __bytes__ returned non-bytes (type bytearray)

* added fixmes about types
* added type hinting

* added cast to Index
* added fixmes about wrong type hinting in uaprotocol_auto.py