altered mail_plugin

- added html + ip option
- updated query's to new query format
added IP-retrieve/validate function to the helper
removed return from the sendmail-foreach loop
little fixes on new mailer plugin
- added missing texts
- allow events with multiple categories
- handle whitespaces inbetween comma separateds lists
- fix typos in _mailer()
mailer plugin: don't mail ip addresses
Merge pull request #676 from jemproject/plugin_mailer

Plugin mailer fixes and enhancements for 1.9.6