Some correction of column names.

Support for internal as well as external users. Added column user_type and used it where necessary

db/migrate/20150818142251_correct_column_names.rb

@@ -0,0 +1,7 @@
+class CorrectColumnNames < ActiveRecord::Migration
+  def change
+	rename_column :request_for_comments, :requestorid, :requestor_user_id
+  	rename_column :request_for_comments, :exerciseid, :exercise_id
+  	rename_column :request_for_comments, :fileid, :file_id
+  end
+end