(chocolatey#2078) Skip importing Chocolatey GUI Extension

The Chocolatey GUI Extension is a "special" extension in the sense that
it isn't intended to work with Chocolatey directly, but it is shipped as
a "normal" Chocolatey extension. We don't want to load the
chocolateygui.licensed.dll into the choco.exe process, but rather leave
it alone, and allow Chocolatey GUI to load it when required.

We are already skipping one existing folder when looking for extension
paths, so this has been extended to include the chocolateygui foler.

src/chocolatey.resources/helpers/chocolateyInstaller.psm1

@@ -1,4 +1,4 @@
-# Copyright © 2017 Chocolatey Software, Inc.
+# Copyright © 2017 Chocolatey Software, Inc.
 # Copyright © 2015 - 2017 RealDimensions Software, LLC
 # Copyright © 2011 - 2015 RealDimensions Software, LLC & original authors/contributors from https://github.com/chocolatey/chocolatey
 #
@@ -58,7 +58,7 @@ if (Test-Path($extensionsPath)) {
   Write-Debug 'Loading community extensions'
   Get-ChildItem $extensionsPath -recurse -filter "*.dll" | Select -ExpandProperty FullName | % {
     $path = $_;
-    if ($path.Contains("extensions\chocolatey\lib-synced")) { continue }
+    if ($path.Contains("extensions\chocolateygui") -Or $path.Contains("extensions\chocolatey\lib-synced")) { continue }
 
     try {
       Write-Debug "Importing '$path'";