Some `/mob.sight` flags are unimplemented

[ike709]

http://www.byond.com/docs/ref/#/mob/var/sight

• [ ] SEE_INFRA
• [ ] SEE_SELF
• [x] SEE_MOBS (#1311)
• [x] SEE_OBJS (#1311)
• [x] SEE_TURFS (#1311)
• [ ] SEE_PIXELS
• [ ] SEE_BLACKNESS
• [ ] BLIND