Stop showing the current project name at the login screen when you aren't logged in (when the project cookie is still hanging around)

• config_defaults_inc.php
  (g_show_project_in_title): remove 3rd possible value. We should compare ON
  and OFF directly, not assume they are 1 and 0. If you don't want the title
  just set it to '' in the window_title and page_title config options

• core/project_api.php
  (project_get_name): new function to get a project name, while handling the
  case of a 0 project_id

• core/html_api.php
  (print_page_top1): stop getting and passing the window_title
  (print_page_top2a): stop getting and passing the page_title
  (print_title): rewrite to be cleaner
  (print_header): rewrite to be cleaner
  (print_footer): update the user's last visit time if they are logged in

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@1824 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9