Rearrange helpers
Allow hidden parameters in filtering form
Basic pagination
Paginate participants in Org connexion
Use explicit URL in filter and pagination forms
Add styling for debugging and technical info
fix the formula for per_page
Assign a variables for filtered participants

Keep all filtered participants in `@filtered_participants` variable.
Show participant count and SQL on the index page
Add a workaround for the ActiveRecord count bug

See https://github.com/rails/rails/issues/9458 for details.