fixes #436 while keeping the constants that are relied on by many parts of the code that access this class without creating an instance of it

changed sidebar menu. #363 Vouchers has its own menu, kit requests is alone now and equipment/rooms/health partners are now inside configuration

added middleware to redirect the user to a confirmation page whenever a study has a privacy_notice assigned, this is enforced and the user haven't accepted yet. superusers excluded

WIP: first draft of privacy notice, go to /privacy_notices to list them and add them, please, create the folder privacy_notices/ before running

addditionally export url requires study_id

additionally subject add url must cointain study id