Improvements related on harvesters

Major improvements:
 * Notification by email
 * Separated log files for each run (associated by history)
 * Clear harvester button to delete all metadata associated

Minor improvements: 
 * ISODate support 
 * Improved batch deletes of metadata (see Clear harvester)
 * Sending mails, now using parameters from ddbb. Not removing MailSender as other classes uses it.