Update space_read.c

** Ignore extra info in BEAM_* and MISSILE_* attributes.
** Don't issue new sdb numbers on load, instead, use the SDB attribute of space objects.
  This means you should use sdb(empty) to get the next free SDB #, and set it on your space object before loading.
  If you destroy objects, reuse the now empty sdb to avoid sdb bloat. (Not that it's really harmful)
** Added our NPC_INFO stuff. You can comment it out if you like.