Several balance adjustments to Dragonblood

[chaosvolt]

Self-PR'd to tinker with and balance further if needed.

• Nerfed the strength and armor bonuses that Sanguine Mark: Manifestation of Strength can dole out.
• Shuffled the armor values of Draconic Scales a bit, and fixed the DDA version not protecting the head any.
• Elemental Affinity now includes a 25% damage vulnerability to anything that deals cold-type damage, which in Arcana tends to be supernatural darkness-themed monsters.
• Added an upgrade to Metabolic Resilence, Metabolic Adaptability. It's a post-thresh version that adds immunity to parasites and food poisoning.
• Stat modifiers have been brought back in, per request. This time it's strength bonuses but dexterity penalties instead of bonuses to both. Replaces the carry capacity modifiers on the wing mutation series.
• Draconic Muzzle and Swept-Back Horns now both add some level of encumbrance when you wear anything over them, consistent with other mutations.
• Toned down the forced encumbrance for the hind limbs mutations to be on par with all the other mutations. This is partly offset by changes to Draconic Plating (see below). In addition, Draconic Hind Limbs in particular gets ways to cancel the penalty for going barefoot. It uses a flag being introduced in the above PR in the BN version, and simply via bringing in Tough Feet in the DDA version since they don't have the barefoot penalty JSONized over there. Also made the movecost modifiers a bit more intense overall.
• Shuffled around the armor values of Swept-Back Horns for consistency.
• Reworked Draconic Plating into an evolution of Draconic Scales, basically combining their effects. It also provides a bit of bonus protection to the mouth (implying it covers the throat mainly), but in exchange it's set up to further encumber several body parts if you wear anything over them, on top of its original token bit of fixed torso encumbrance.
• Reflavored Savage Instinct into Monstrous Form, with it adding a mix of physical changes along with the mental changes. Notably it flags you as counting as Large (in DDA version, BN version TBD), and adds a on-hit effect that gives your attacks a 5% chance of added knockdown.

[chaosvolt]

Due to severe scope drift in https://github.com/cataclysmbnteam/Cataclysm-BN/pull/1486 leading me to working on changes that'll take much more work to be ready, I've removed the size upgrade effect from Monstrous Form in the BN version, so I'll be able to merge this independently.