core: Show what machine error messages are for [GH-1668]

lib/vagrant/environment.rb

@@ -420,6 +420,7 @@ module Vagrant
         level  = config_errors.empty? ? :warn : :error
         output = Util::TemplateRenderer.render(
           "config/messages",
+          :name => name,
           :warnings => config_warnings,
           :errors => config_errors).chomp
           @ui.send(level, I18n.t("vagrant.general.config_upgrade_messages",

templates/locales/en.yml

@@ -77,7 +77,9 @@ en:
 
         %{message}
       config_upgrade_messages: |-
-        There were warnings and/or errors while loading your Vagrantfile.
+        There were warnings and/or errors while loading your Vagrantfile
+        for the machine '%{name}'.
+
         Your Vagrantfile was written for an earlier version of Vagrant,
         and while Vagrant does the best it can to remain backwards
         compatible, there are some cases where things have changed