Fix wrong layout option for utility tab contents
Fix 'filtering_form' helper
'approve!', 'disapprove!' instead of 'approved='
Add Participation#talk_proposed virtual attribute
Add a utility tab: participant who proposed talks
Change the application directory structure
Use "nested layouts" to render tab contents

I have found a way to use really nested layouts (in the natural sense, not in the sense of Ruby on Rails). It seems natural to use them to render tab sontents inside a page which serves moslty as a layout (the Utilities page for organisers).
Mark organiser interface with an HTML class

Put all elements of the organiser interface inside tags with 'organiser_interface' HTML class.
Use different font for elements of Org interface
Set the basic font size to 18px (instead of 100%)
Change organiser interface views
Separate views for participants with short talks
Reduce the basic font size 18px -> 16px
Fix default string encoding problems
Restrict allowed values of academic_position
Work on filtering form
Improve SimpleRelationFilter

Improve SimpleRelationFilter, allow arrays of strings.
Allow to filter participants by academic_position

Allow to filter participants by academic_position in organizer connexion.