Add shell_plugins to abstract shell-specific functions out of runner, add winrm connection plugin, add initial Windows modules.

library/windows/command.ps1

@@ -0,0 +1,13 @@
+#!powershell
+# WANT_JSON
+
+If ($args.Length -gt 0)
+{
+   $params = Get-Content $args[0] | ConvertFrom-Json;
+}
+
+$data = 'FIXME';
+
+$result = '{}' | ConvertFrom-Json;
+$result | Add-Member -MemberType NoteProperty -Name fixme -Value $data;
+echo $result | ConvertTo-Json;