remove old model
Merge pull request #334 from differentreality/event_person_delete

remove old model
fix event type naming
fix tests for event types
rework roles with rolify
authorization with cancancan
set up abilities
fix proposal
fix conference registration
add necessary validations for event_attachment
check abilities
add is_admin attribute to users
use single ability model
verify user if accessing admin area. Testing: setup organizer_conference_1_role
fix redirect error after sign_in
rework users page, add role assignment