- st_death add new subkind "st_death_movable":
- can be pushed by protected and death proven actors, per wire and all
stoneimpulses like rotator, lightpassenger,...
- new attribute "interval", default 10 seconds, defines the average time
interval between two animations - this allows user to locate movable death,
value of 0.0 switches the anim off
- movable death will show in lighter gray when seen through glasses.
- death can be moved by pushing st_boulder, too
- identify Lua datatypes "default", "maze" and "cell"