Remove dead code in metadata models.py
Move file storage functions in their own file
Create a correct document urls structure
Upgrade document models to embed different metadata types
Typo
Remove useless import
Error in import
Typo
Add Transmital document type to document models
Use natural key on document metadatas
Reminder to add global document fields as cache.

Those fields will be used for favorites and such features.
{created,update}_on fields on Metadata variations
Update ConfigurableChoiceField API

Put "list_index" in kwargs so it doesn't have to be passed as first
parameter.
Create the (hopefully) correct document metadata api
Link to correct classes in fixtures
Bump django version
Correct urls.py syntaxes
Upgrade initial documents fixtures
Add categories in document fixtures
Use natural keys for documents