Add CEntityHandle which wraps an entity_id_t and also has a pointer to a
per-entity array of IComponents. QueryInterface/CmpPtr on a handle just
involve a couple of pointer dereferences instead of a map lookup.
This requires sizeof(void*) per registered interface type per entity,
which is currently ~0.5KB per entity, which shouldn't be a problem.
This was SVN commit r13825.
Make 'delete' command kill the unit instead of destroying it.
Make projectiles vanish after a timeout.
Fix projectile landing positions with low framerates.
This was SVN commit r7837.
