Enable SSPI Support for Postgres SQL

[dylan_morgan]

Add capability of using SSPI for Windows Authentication in Postgres SQL. https://www.postgresql.org/docs/9.4/static/auth-methods.html

[Samuel_Ferguson]

Apparently this was only "a few months away" back in November 2016. However we're still waiting... https://community.powerbi.com/t5/Integrations-with-Files-and/Error-Message-Connecting-to-PostgreSQL-using-SSPI/td-p/76549