1. First shot at sitewide admin ui for global parameters. You can edit them
from the sitewide admin page list that was previously built for packages
that have a sitewide-admin subdirectory. Package is now displayed for
either the existence of sitewide-admin or global parameters.
2. Did something I'd wanted to do for some time. When Nima added the
parameter_changed callback in acs subsite, he actually *moved* the
set_value call there. I've changed it so it more rationally sets the
value in the parameters page, then calls the parameter_changed callback.
3. Invented a global_parameter_changed callback that works as the regular
parameter_changed callback. This was necessary to avoid breaking existing
uses of parameter_changed.
More testing is required before release (which will hopefully happen
tomorrow, Sunday Apr 4).
