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/views/tracks/show.html.haml

@@ -0,0 +1,26 @@
+.container
+  .row
+    .col-md-12
+      .page-header
+        %h1
+          = @track.name
+          Track
+  .row
+    .col-md-8
+      %dl.dl-horizontal
+        %dt
+          Color:
+        %dd
+          %span.label{style: "background-color: #{@track.color}; color: #{ contrast_color(@track.color) }"}
+            = @track.color
+        %dt
+          State:
+        %dd
+          = @track.state
+        %dt
+          Description
+        %dd
+          = @track.description
+  .row
+    .col-md-12.text-right
+      = link_to 'Edit Track request', edit_conference_program_track_path(@conference.short_title, @track.short_name), class: 'btn btn-primary'