Use named route with attachment filename for inline images.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11189 e93f8b46-1217-0410-a6f0-8f06a7374b81
Use helper.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11190 e93f8b46-1217-0410-a6f0-8f06a7374b81
Attachment name is added in the generated link.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11191 e93f8b46-1217-0410-a6f0-8f06a7374b81