Change the app_usages API to accept array of data

- Add foreignkey to device for AppUsage
- Rename the route to app_usage from app_usage/create

config/routes.rb

@@ -1,5 +1,5 @@
 Rails.application.routes.draw do
-  post 'app_usages/create', to: 'app_usages#create', :defaults => { :format => :json }
+  post 'app_usages', to: 'app_usages#create', :defaults => { :format => :json }
 
   devise_for :admin_users, ActiveAdmin::Devise.config