Skill multipliers addition and refactoring

[ze-dom]

To-do

• [x] Comment changes with references
• [x] Create UpdatePlugins (after discussion)

Developments

• Added skill-specific multipliers and bonuses
• Added Weakness magic effect

Bugfixes

• Elf skills multipliers
• RF's Increase Health skill target attribute

There is still quite some work to do to finalize the Rage Fighter skills. They are lacking some particular magic effects and I don't think all of them have the correct number of hits.