Missing effect implementations

[kennyvv]

A lot of effects, like nightvision have not yet been implemented.

For nightvision we should allow setting something like a skylight offset on our rendering shaders otherwise we'd need to rebuild all chunks everytime the effect is applied or removed.

The following effects have yet to be implemented (and possibly more) Contributions are welcome!

• [ ] Night vision
• [x] Slowness
• [ ] Haste
• [ ] Mining Fatigue
• [ ] Strength
• [ ] Instant Health
• [ ] Instant Damage
• [ ] Nausea
• [ ] Regeneration
• [ ] Resistance
• [ ] Fire Resistance
• [ ] Water Breathing
• [ ] Invisibility
• [ ] Blindness
• [ ] Hunger
• [ ] Weakness
• [ ] Poison
• [ ] Wither
• [ ] Health Boost
• [ ] Absorption
• [ ] Saturation