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

(workaround e1c168d of Apr 22 is reverted)
- 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 (and doesn't contain such key)