<message> tags can now contain sprintf() format
strings (%d, %.2f etc), with
<message-param>
<property>/some/prop</property>
</message-param>
used as the substitute value. Could be extended
in the future with perhaps Nasal evaluation?
When user switched to a different view mode (e.g. chase/helicopter/tower
view) before or during a tutorial, everything went wrong...
Need to control (save/restore/switch) the view number (view mode) during
tutorials. Also adds an option to explicitly change view mode during
a tutorial, i.e. tutorials can switch to tower view, chase view, ... now.