Notifications: edited log messages for emails

- message, which is logging sending of emails was edited, so that there was
  useful information in logfile perun-notif-sended.log
Notifications: fixed removing regex from template

- the regex is now removing also from the cached memory of all templates
Merge pull request #600 from jirmauritz/notification

Notifications: logging of sent emails and fixed bug in removing regex from template
Merge pull request #600 from jirmauritz/notification

Notifications: logging of sent emails and fixed bug in removing regex from template
All changes from 'master' to 'production'