Fix HUGE MEMORY LEAK in do_space_db_read()

** We now mush_free() the arrays as we use them. (Imagine that!)
** We no longer complain if we get more than we expect for BEAM_ or MISSILE_ attributes.
** We use the SDB number in the space object's attributes, rather than the next free one.
** Loads our warp_afford and impulse_afford attributes.