Write first version of ImageCleaner for #1502

Write to file and add worker

app/objects/service/image_cleaner.rb

@@ -0,0 +1,39 @@
+#   Copyright (c) 2012-2016, Fairmondo eG.  This file is
+#   licensed under the GNU Affero General Public License version 3 or later.
+#   See the COPYRIGHT file for details.
+
+class ImageCleaner
+  def initialize
+  end
+
+  def show(range)
+    files_found = 0
+
+    File.open('image_cleaner.txt', 'w') do |file|
+      for id in range
+        path = path(id)
+
+        begin
+          img = Image.find(id)
+          file.puts("#{path}: #{img.image_file_name}")
+        rescue ActiveRecord::RecordNotFound
+          if File.exist?(path)
+            files_found += 1
+            file.puts("#{path}: no image")
+          end
+        end
+      end
+
+      file.puts("Extranous files total: #{files_found}")
+    end
+  end
+
+  def path(id)
+    id_str = padded_id(id)
+    Rails.root.join('public', 'system', 'images', id_str[0..2], id_str[3..5], id_str[6..8])
+  end
+
+  def padded_id(id)
+    sprintf('%09d', id)
+  end
+end

app/workers/image_cleaner_worker.rb

@@ -0,0 +1,16 @@
+#   Copyright (c) 2012-2016, Fairmondo eG.  This file is
+#   licensed under the GNU Affero General Public License version 3 or later.
+#   See the COPYRIGHT file for details.
+
+class ImageCleanerWorker
+  include Sidekiq::Worker
+
+  sidekiq_options queue: :default,
+                  retry: 20,
+                  backtrace: true
+
+  def perform(range)
+    cleaner = ImageCleaner.new
+    cleaner.show(range)
+  end
+end