made email field available for creating and edit a participant [Finishes: #70764746]
User can create participant with or without a study_id [Finishes: #70464970]
log out Users and Participants after 20 minutes of inactivity [Finishes #61084340]
refactored Ability
add specs and set TaskStatus completed_at correctly [Finishes #70701470]
cleaned up rails admin [Finishes #70697584]