Improvement: Elemental DoT debuffs (choke, burn, etc) need power to affect hp/tic and subpower to affect -stat

[tankfest]

I have:

• [x] searched existing issues (http://project-topaz.com/issues/) to see if the issue has already been opened
• [x] checked the commit log to see if the issue has been resolved since my server was last updated

Additional Information (Steps to reproduce/Expected behavior) :

Currently all 6 ele DoT spells use a singular ratio to determine both their hp/tic loss and -stat loss from the effect's power variable. We need the -stat loss to be taken from the subpower so it is configurable independently of the -hp/tic. The ratio we have currently should ONLY be used if the subpower is not provided, it would default to the ratio.

@TeoTwawki has input on this too from talking to him several times about it.

[TeoTwawki]

Like tank said, I think we should be able to simply specify what we want, power for dot subpower for stat down, and fall back to the current behavior when we do not:

target:addMod(tpz.mod.REGEN_DOWN, effect:getPower())
target:addMod(tpz.mod.STR, -getElementalDebuffStatDownFromDOT(effect:getPower()))

function getElementalDebuffStatDownFromDOT(dot)
    local stat_down = 0
    stat_down = (dot-1)*2 +5
    return stat_down
end