[Gameplay] Knockbacks that target a point rather than being a vector with a direction create issues

Things like Jayce knockback and Singed/Voli flips work in this fashion, though there was a fix some time ago so the flip wouldn't work against flash most of the time. The way it works is rather than a spell sending an enemy X units toward point X the game just tries to send an enemy to point X, this causes issues.

https://www.youtube.com/watch?v=yowHJTRRO60 http://www.youtube.com/watch?v=VmwzZw_MUew&feature=youtu.be

The one with Fiddle is a combination of that bug and this one http://boards.na.leagueoflegends.com/en/c/bug-report/ixN2rAJT-gameplay-actions-only-checking-conditions-on-the-first-cast-and-not-on-the-end-animation