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

app/models/user.rb

@@ -55,6 +55,7 @@ class User < ActiveRecord::Base
   has_many :votes, dependent: :destroy
   has_many :voted_events, through: :votes, source: :events
   has_many :subscriptions, dependent: :destroy
+  has_many :tracks, foreign_key: 'submitter_id'
   accepts_nested_attributes_for :roles
 
   scope :admin, -> { where(is_admin: true) }