[Bugfix] Confirmed / Unconfirmed events over time for conference dashboard
Merge pull request #297 from ChrisBr/bugfix_events_over_time_new

 [Bugfix] Confirmed / Unconfirmed events over time for conference dashboard
Added nil checks for call for papers in event index
Changed first / lastname to name

close #342
close #344
Merge pull request #345 from ChrisBr/bugfix_events_index

Added nil checks for call for papers in event index
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
do not allow access to admin area if user does not have a relevant role
verify_user first, before authorizing resources, so that users are first prompt to sign in, instead of being presented with an 'access denied' error message.