misc #2:

make sure ALL LuaSynced* weapon API functions are 1-based;
use a #define for the choice between 0- and 1-based indices
and update unit_script.lua since it does not need to correct
them for SetUnit*State anymore (note: the same should be done
for piece indices)

NEXT TIME *THINK* ABOUT A CHANGE LIKE THIS LONG AND HARD BEFORE YOU MAKE IT!

reduce target-lost CAI timeout from 8 to 2 seconds

unhardcode some magic numbers in HoverAirMoveType