Feature Request: Add Authentication setting per instance rather than Global

[gautamsi]

Authentication API should register Authentication provider, Once registered, new instance of ExchangeService can use them per instance,

This helps in using basic authentication and NTLM authentication in same nodejs project.

[gautamsi]

You can now use this per instance of ExchangeServiceBase (ExchangeService and AutodiscoverService).

use ConfigurationApi.ConfigureXHR to configure this globally. when want to override modify using

service.XHRApi = new ewsAuth.ntlmAuthXhrApi(credentials.userName, credentials.password)

where service is ExchangeService or AutodiscoverService

[gautamsi]

0.9 dev7 published, re-open if you face any issue., also closes gautamsi/ews-javascript-api-auth#2