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/_form.html.haml

@@ -0,0 +1,17 @@
+.container
+  .row
+    .col-md-12
+      .page-header
+        %h1
+          - if @track.new_record?
+            New
+          = @track.name
+          Track
+  .row
+    .col-md-12
+      = semantic_form_for(@track, url: (@track.new_record? ? conference_program_tracks_path : conference_program_track_path(@conference.short_title, @track.short_name))) do |f|
+        = f.input :name
+        = f.input :short_name, hint: "A short and unique handle for the track, using only letters, numbers, underscores, and dashes. This will be used to identify the track in URLs etc. Example: 'my_awesome_track'", input_html: { required: 'required', pattern: '[a-zA-Z0-9_-]+', title: 'Only letters, numbers, underscores, and dashes.' }
+        = f.input :color, input_html: {size: 6, type: 'color'}, required: true
+        = f.input :description, input_html: {rows: 2, data: { provide: 'markdown-editable' } }, required: true, hint: markdown_hint
+        = f.action :submit, as: :button, button_html: { class: 'btn btn-primary' }