Revert "Wall spell fixes"

This reverts commit 7b0c4566c42b6a7346673f3ba8dc8479ecd72578.
Wall Spells - dont kill & delete if caster logs

Added a new parameter to Player's AssessDamage function in order to
accomodate new behavior: wall spells no longer kill players, instead
leaving them at 1 hp. Other future spells can use the dont_kill
parameter for the same effect.

Also, active wall elements will delete themselves if their caster logs
off.