Used a Pillow requirement lower than 2.0.0 as it doesn't build with Python 2.5 anymore.
Merge branch 'master' into develop
Implemented a widget that shows a clear checkbox for any non-required form field.
Overriden admin widgets of CharFields and TextFields and patched forms.CharField for nullable fields, so undefined translations don't get filled with empty strings when an admin form is saved (thus becoming defined in the case of a nullable field).
Merge branch 'feature/no-empty-string-fallback-for-nullable' into develop
Merge branch 'feature/no-empty-string-fallback-for-nullable' into feature/non-nullable-translation-fields
Made translation field "nullability" same as the original field and fixed a couple of tests.
Now the field's default value is the value saved as the "no translation" value, nevertheless translations are still not required.
Merge branch 'feature/non-nullable-translation-fields' into develop