Modus Veritas

I couldn't really find any data on what the miss rate is, so I just used
an existing ability resistance function. Also, I prevented it from
stacking more than a couple times to prevent 18 SCH shenanigans.
Added Modus Veritas, helix fix

Helixes DOTs were doing 0 damage if the initial spell got eaten by
stoneskin.
Modus Veritas not on NMs
Merge pull request #311 from Jupiter065/modus_veritas

Modus veritas & helix fix