- add <marker> support (blinking magenta circle to point to switches etc.)
- use "real" conditions instead of tutorial-only ones
- list of <error> with <message> and <condition> children, instead
of one <error> group with <check> items (necessary because of <condition>)
- only one <exit> (use <condition><and>... to define a set
- rename properties <prop><val><msg> to <property><value><message>
(consistency with other systems)
- <end><message>/<voice> instead of <endtext> and <endtext-voice> etc.
- add <nasal> support everywhere, with separate namespace and predefined
tutorial functions in it (currently only say(), next(), previous())
- make <timeofday> property actually work
TODO:
- more cleanup/re-organization
- add optional <view> group, to direct user view to switches (for startup
tutorials etc.)
2-space indentation changed to tabs (with Stuarts permission), and braces
to K&R style (rationale on request :-)
