Fix a model association
Fix model_presentation_helper

Do not try to process nil values.
Fix participation ordering
Edit only selected participant attributes

Allow to edit only selected participant attributes and associations.
Simplify updating nested participant attributes
Simplify updating nested participant attributes

More simplification.
Simplify updating nested participant attributes

Even more simplification.
Improve editing participant and nested attributes
Move "accept/not accept" button into folding
Add a talk_proposal association translation
Move participations and talk_proposal to partials

Move participations and talk_proposal of a participant in participant index to partials.