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

db/migrate/20170705075039_add_state_cfp_active_and_submitter_reference_to_tracks.rb

@@ -0,0 +1,8 @@
+class AddStateCfpActiveAndSubmitterReferenceToTracks < ActiveRecord::Migration
+  def change
+    add_column :tracks, :state, :string
+    add_column :tracks, :cfp_active, :boolean
+    add_column :tracks, :submitter_id, :integer
+    add_index :tracks, :submitter_id
+  end
+end