- use templates for signin form, error messages

- use templates for signin form, error messages
- use FormBuilder for edit page forms (also use template)
- print debug to stderr in cgi mode to avoid breaking http headers
- fix links to page in parentlinks if $url is unset
- reorganise how wikilink is used in templates
- only make recentchanes link if svn is enabled
- change session id cookie to something we control
- add support for logging committer name for web commits from signed in
  users (untested)
- probably more changes I forgot