- validate version_ids in page-contract
- parameter page: make setting of context for instance and global parameter uniform
- provide link from package instance parameters page to global page in
  case global parameters exist
- provide backlink when global parameters are called from /acs-admin/index.tcl
- Don't use util_user_message to provide feedback for newly registered
   users. util_user message is used for "ad_returnredirect  ... -message",
   which was used to report back to the user that some actions are required.
   If RegistrationRequiresEmailVerificationP or
   RegistrationRequiresApprovalP  is set, a newly registered users is
   logged out immediately after filling out the form. Therefore,
   session_id is reset, and util_user_message (that depends on the
   session_id) fails to deliver the content. We use now
   "ad_return_warning" which does not have this problem.
 - Provide a mechanism, that util_user_messages are not swallowed in
   return redirects. When ad_returnredirect sets a util_user_messages
   it is now safely provided at the target page.
- reduce verbosity