Merge pull request #2191 from yakky/feature/lang_copy

Add copy-lang command
fixes a bug where you remove a language and you still have content in it from that language
Merge branch 'develop' of github.com:divio/django-cms into develop
First implementation of frontend-editable models
Add language
Better language handling
Remove debug from template
Test WiP
Fix placeholder tests
Documentation WiP
Add callable as allowed item target
Documentation
Add tests for callable items and item from context in 'show_editable_model'
Edit documentation
Edit documentation
Fix typo
The Helsinborg commit.
The templatetag now accepts view urls as parameters to be linked.
Added admin base class to edit single fields in a model from the frontend
The Stockholm commit.
Edit comment in code
The Göteborg commit.
Remove custom test templates. Add test for custom urls and single field edit.
The Bamberg commit.
Edit documentation.