Populate RemoteIpAddress and RemotePort on HttpContext.Connection

[Marcus-L]

Fixes #22

Allows the AspNetCore application to access the remote client ip/port information via HttpContext.Connection, which works when running locally via dotnet run.

RemoteIpAddress is obtained from the APIGatewayProxyRequest's RequestContext.Identity.SourceIp
RemotePort is obtained from the APIGatewayProxyRequest's Headers["X-Forwarded-Port"]

For example this would allow for a WebAPI Controller to use the remote info:

[HttpGet]
public string GetRemote()
{
    var c = HttpContext.Connection;
    return $"{c.RemoteIpAddress}:{c.RemotePort}";
}

Updated the test input to provide the source IP, did not add the header "X-Forwarded-Port" in case a better place to get port information from is known by the maintainer.

[normj]

Thanks for the pull request. I have this merged in a local branch. I'm trying to finish off a couple more things first and then I'll do a release with this change and close out this pull request.