Add an SQLA model mixin for file uploads
Add a BinaryData Colander type for file uploads
Add a custom FileUploadWidget
Add photo upload to Pully form
CSS for file upload fiels

We add color: #000000 so that "No file chosen" or the file name is visible in the page.
Add tests for BinaryData type
Now fr translations for pully
Fix updating a form with files
Use db entity to show form

Otherwise the PKs of entities in relations might not be set.
Merge pull request #39 from elemoine/photo-upload

Photo upload