Add option to authenticate via refresh token

[WebSpider]

This implements the option to start an authenticated session via an OIDC/Oauth2 refresh token, in preparation for the homeassistant integration to start storing the refresh tokens, speeding up authentication since we no longer have to do the Oauth2 dance via webforms.

This PR changes the auth/authorize() and the connect() call in the following ways:

• You need to specify either email+password or refresh_token
• If you specify email+password, nothing changes
• If you do not specify email+password, but specify refresh_token, the token will be used to retrieve a new acces token, granting access

Since the refresh_token argument is not the first argument, you can not call MySkoda.connect('tokencontent'), you now need to specify that you are sending a refresh_token as argument.

Options to authenticate are:

1. Regular username/password authentication:

This can be

MySkoda.connect('username','verysecrethush`)

which is backwards compatible

OR

MySkoda.connect(email='username',password='verysecrethush`)

2. Using a refresh token you need to specify you are using a refresh token. Otherwise we silently assume you send email/password.

MySkoda.connect(refresh_token='tokencontent')

The result will be the same: The library will connect and authenticate/authorize based on the credentials sent. With the authenticated MySkoda object you can perform all other calls next.

[WebSpider]

@dvx76 I'd like your opinion about this approach. Should we make changes to existing methods, or make new ones?