Can not upgrade behind a proxy server that requires credentials

[stajs]

Title

Can not upgrade behind a proxy server that requires credentials.

Functional impact

There seems to be a bug with upgrading behind a proxy server.

Minimal repro steps

I'm on dnvm v1.0.0-beta8-15506 (latest at time of writing).

1. Use a network connection with a proxy server that requires credentials.
2. Specify a proxy server argument to upgrade: dnvm upgrade -Proxy <server>:<port>

Expected result

Should upgrade okay.

Actual result

Fails to upgrade.

Determining latest version
Unable to find any runtime packages on the feed!
At C:\Users\<user>\.dnx\bin\dnvm.ps1:584 char:9
+         throw "Unable to find any runtime packages on the feed!"
+         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : OperationStopped: (Unable to find ...es on the feed!:String) [], RuntimeException
    + FullyQualifiedErrorId : Unable to find any runtime packages on the feed!

Further technical details

The -Proxy parameter is not being passed to the method calls Find-Latest and Invoke-NuGetWebRequest. Editing C:\Users\<user>\.dnx\bin\dnvm.ps1 line 1335 from:

$findPackageResult = Find-Latest -runtimeInfo:$runtimeInfo -Feed:$selectedFeed

... to:

$findPackageResult = Find-Latest -runtimeInfo:$runtimeInfo -Feed:$selectedFeed -Proxy:$Proxy

... produces a much more pleasing:

Determining latest version
'dnx-clr-win-x86.1.0.0-beta7' is already installed in C:\Users\<user>\.dnx\runtimes\dnx-clr-win-x86.1.0.0-beta7.
Adding C:\Users\<user>\.dnx\runtimes\dnx-clr-win-x86.1.0.0-beta7\bin to process PATH
Adding C:\Users\<user>\.dnx\runtimes\dnx-clr-win-x86.1.0.0-beta7\bin to user PATH
Updating alias 'default' to 'dnx-clr-win-x86.1.0.0-beta7'

Also, you might as well also add the proxy on line 1338, from:

$findPackageResult = Find-Package -runtimeInfo:$runtimeInfo -Feed:$selectedFeed

...to:

$findPackageResult = Find-Package -runtimeInfo:$runtimeInfo -Feed:$selectedFeed -Proxy:$Proxy

This was originally reported (issue, PR) in the Home repo; moved to dnvm repo by request.