Add support for PostgreSQL connections with certificate

[HartmutT]

Some PostgreSQL servers use client certificates to authenticate database clients. Recent Npgsql versions add support for this authentication mode; only Npgsql 6.x fully supports it by adding extra parameters such as the certificate path to the connection string. While GISquirrel cannot reference Npgsql 6.x due to .Net framework incompatibilities, the .Net 4 builds (ArcGIS 10.4 and higher that reference Npgsql 2.2.7) can add the "Trust Server Certificate" parameter to the connection string, which instructs Npgsql to trust the server certificate without validating it. This is not ideal, but at least it allows connections to these servers to be made from ArcGIS Desktop. ArcGIS Pro should be compatible with Npgsql 6.x.

[HartmutT]

Fixed in build 1.3.5482, tested by James Mitchell, you first identified the issue.