UI/UX changes related to tracks

Add confirmed and cfp_active scopes to Track
Render markdown in track's description
Make the views more similar to the proposal/events views
Change the sequence of columns in admin/Tracks#index
Remove the short_name column from the index views
Add button "My Tracks" in the user menu
Fix track count in proposals
Add details of track in admin/Tracks#show
Use tabs to show track details and events

app/models/track.rb

@@ -32,6 +32,9 @@ class Track < ActiveRecord::Base
 
   before_validation :capitalize_color
 
+  scope :confirmed, -> { where(state: 'confirmed') }
+  scope :cfp_active, -> { where(cfp_active: true) }
+
   state_machine initial: :pending do
     state :new
     state :to_accept