Add option for Autobind

[mattrobineau]

Is your feature request related to a problem? Please describe. There seems to be missing an option to specify the Autobind value. This might be a result of my ignorance on the subject of LDAP. I am specifically referring to this property (also mentioned here).

Describe the solution you'd like Support for Autobind or a workaround.

[flamencist]

I think its not necessary. You could replace AutoBind by Bind method. For your second link you could use ConnectI and External Auth bind - https://github.com/flamencist/ldap4net#bind-sasl-external-unix-socket