mailer plugin: on empty body text try with ip (related to #676)
mailer: choose name OR username, changed name of changed texts

- depending on component's global setting user's name OR username (loginname) is used
- all mail body have changed as required to have matching "%s" count
- text keys have changed: number of params expected attached (as hex :wink:)
  so en-GB will be used if additional language pack is too old
Merge pull request #682 from jemproject/plugin_mailer

mailer: choose name OR username, changed name of changed texts (related to #676)