Adds a specific error message for when the start date is too earlier than the minimum start date (#14086).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11926 e93f8b46-1217-0410-a6f0-8f06a7374b81
Adjusts error message in tests (#14086).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11927 e93f8b46-1217-0410-a6f0-8f06a7374b81
Really adjusts error message in tests (#14086).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11928 e93f8b46-1217-0410-a6f0-8f06a7374b81