tweak msg creations and use url_for method to generate urls

It's a tweak commit for me. if you like it, merge it.

it has 3 things: 
  * change the msg format to: "WHO WHAT WHEREWITH : MSG (URL)". sometimes msg are empty, then that is omitted
  * use redmine truncate_single_line method to truncate the long lines.
  * url_for method to generate urls