Fixed: Unable to add plugin

Fixes bug which made it impossible to add plugins, with placeholder.pk>=1000. Reason was, that placeholder.pk got a thousand separator.
Merge branch 'master' of https://github.com/divio/django-cms
Merge remote-tracking branch 'upstream/master'

Conflicts:
	cms/templates/admin/cms/page/widgets/plugin_editor.html
Merge remote-tracking branch 'upstream/master'
Merge branch 'add-method-is_parent_required' of ssh://github.com/jrief/django-cms into add-method-is_parent_required