plone.app.multilingual support on Plone 5

[keul]

Following #11

---

Right now a portletpage can't be transalted with plone.app.multilingual + archetypes.multilingual:

Traceback (innermost last):
  Module ZPublisher.Publish, line 138, in publish
  Module ZPublisher.mapply, line 77, in mapply
  Module ZPublisher.Publish, line 48, in call_object
  Module Products.ATContentTypes.tool.factory, line 493, in __call__
  Module ZPublisher.mapply, line 77, in mapply
  Module ZPublisher.Publish, line 48, in call_object
  Module Products.CMFFormController.FSControllerPageTemplate, line 91, in __call__
  Module Products.CMFFormController.BaseControllerPageTemplate, line 32, in _call
  Module Shared.DC.Scripts.Bindings, line 322, in __call__
  Module Shared.DC.Scripts.Bindings, line 359, in _bindAndExec
  Module Products.CMFCore.FSPageTemplate, line 237, in _exec
  Module Products.CMFCore.FSPageTemplate, line 177, in pt_render
  Module Products.PageTemplates.PageTemplate, line 87, in pt_render
  Module zope.pagetemplate.pagetemplate, line 132, in pt_render
  Module five.pt.engine, line 98, in __call__
  Module z3c.pt.pagetemplate, line 163, in render
  Module chameleon.zpt.template, line 261, in render
  Module chameleon.template, line 191, in render
  Module chameleon.template, line 171, in render
  Module d0e2546378ac57e4f5025b1079269dfd.py, line 1757, in render
  Module d0e2546378ac57e4f5025b1079269dfd.py, line 1574, in render_master
  Module 155aee19a020fb6455f61f3f27483632.py, line 1223, in render_master
  Module 155aee19a020fb6455f61f3f27483632.py, line 458, in render_content
  Module d0e2546378ac57e4f5025b1079269dfd.py, line 1562, in __fill_main
  Module d0e2546378ac57e4f5025b1079269dfd.py, line 599, in render_main
  Module five.pt.expressions, line 141, in __call__
  Module Products.PageTemplates.Expressions, line 117, in render
  Module plone.app.multilingual.browser.utils, line 154, in current_language_name
AttributeError: 'NoneType' object has no attribute 'get'

 - Expression: "pamutils/current_language_name"
 - Filename:   ... tilingual/skins/archetypesmultilingual/at_babel_edit.cpt
 - Location:   (line 129: col 73)
 - Source:     ... " tal:content="pamutils/current_language_name" tal:omit-tag= ...
                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 - Arguments:  repeat: {...} (0)
               template: <ImplicitAcquisitionWrapper at_babel_edit at 0x115ac2a00>
               modules: <instance - at 0x112752f38>
               here: <ImplicitAcquisitionWrapper portlet_page.2016-07-15.2674907904 at 0x115ac2cd0>
               user: <ImplicitAcquisitionWrapper - at 0x115969370>
               nothing: <NoneType - at 0x10fa3ef98>
               container: <ImplicitAcquisitionWrapper Plone at 0x116063be0>
               default: <object - at 0x10fb80c00>
               request: <instance - at 0x11894ae18>
               wrapped_repeat: <SafeMapping - at 0x118b82838>
               traverse_subpath: <list - at 0x1183ed6c8>
               loop: {...} (2)
               context: <ImplicitAcquisitionWrapper portlet_page.2016-07-15.2674907904 at 0x115ac2cd0>
               translate: <function translate at 0x11705d500>
               root: <ImplicitAcquisitionWrapper Zope at 0x1153771e0>
               options: {...} (2)
               target_language: <NoneType - at 0x10fa3ef98>