Merge branch 'easily-add-new-formset-to-product-update-page' into machtfit

* branch easily-add-new-formset-to-product-update-page:
  Provide a hook for cross-form validation
  Make it trivially easy to add more formsets to the product update page
  Unify __init__ method signature of formset classes
  customize FormSet class after calling inlineformset_factory
  Whitespace, Formatting, PEP8

https://github.com/tangentlabs/django-oscar/pull/1022
Merge branch 'contain-productimages-z-index' into machtfit

* branch contain-productimages-z-index:
  Create a new stacking context for the freakishly large z-index values used in upload-images

https://github.com/tangentlabs/django-oscar/pull/1030
Merge branch 'dashboard-fix-custom-permissions' into machtfit

* branch dashboard-fix-custom-permissions:
  For core oscar views get the corresponding application using loading.get_class

https://github.com/tangentlabs/django-oscar/issues/993
https://github.com/tangentlabs/django-oscar/pull/1034