Buffs bonus could be configurable as percentage

[walt253]

Currently those are hardcoded. Raising an issue so it's not forgotten.

I might pick this up later but for now I need opinions.

We have to decide what would be the best way for it:

1/ rules.cfg is the simplest way code-wise but less intuitive for modders. 2/ magic.cfg is not harder to do but for effects that do differents things you need more fields, this could be confusing for modders too, for example Speed affects 3 things: Cooldown of abilities, MovSpeed and Working values.

So adding 3 fields for Speed on [magic] block of rules.cfg is overall less confusing I think, but let me know what you think of it.