Implement track requests and add the track organizer role

About track requests:
Create migration that adds the fields submitter_id, state, and
cfp_active to Tracks
Add validations and the self_organized? method to the Track model
Create a new TracksController outide of the admin namespace
Create the relevant views for index, show, new and edit
Modify the admin views for tracks to include extra info for
self-organized tracks

About track organizers:
Create the role when a self-organized track is created
Define track organizer abilities
Modify the roles views and controller to handle the new role

The route for Roles#edit needs to have higher priority than the nested
routes for track roles, otherwise, the word edit in the url is matched
as a track with short_name edit

.rubocop_todo.yml

@@ -94,6 +94,8 @@ Metrics/ModuleLength:
 # Offense count: 14
 Metrics/PerceivedComplexity:
   Max: 15
+  Exclude:
+    - 'app/controllers/admin/roles_controller.rb'
 
 # Offense count: 11
 # Cop supports --auto-correct.
@@ -850,6 +852,7 @@ Style/SymbolProc:
     - 'app/controllers/admin/questions_controller.rb'
     - 'app/helpers/application_helper.rb'
     - 'app/models/ability.rb'
+    - 'app/models/admin_ability.rb'
     - 'db/migrate/20140730104658_migrate_roles_for_cancancan.rb'
     - 'spec/controllers/admin/conferences_controller_spec.rb'
     - 'spec/support/flash.rb'