Damage calculations refactoring

[ze-dom]

Still to do:

• [x] Comment changed files with rationale & source references
• [ ] Update plugins (after discussion)

Changes

• Damage calculations reviewed end to end (related jewelry and pet items to come in future PR)
• Added Elf's melee dmg logic
• Added Elf's bolts/arrows dmg increase
• Added "double wield" logic
• Added DL skills dmg attribute relationships
• Added Sum's Berserker magic effect
• Added Sum's curse/wizardry dmg calcs/attribute relationships
• Added ancient jewelry bonus attribute damage

Bugfixes

• Fire socket option
• Excellent +2% dmg options
• MG can now equip a staff on RH
• Removed Powerslash skill energy requirement

Notes

I followed the damage calculation sequence in zTeamS6.3 and emu sources and tried to keep things relatively close whenever possible (as usual, with some compromises here and there).

The original Summoner damage calculations seem to diverge a bit from the more "classical" ones (with its own specific method), which gave rise to a few more if's here and there :smile:. Anyway, let's discuss and seek out the possible better final product!