Fixed IsActive query returning incorrect value

Active upgrades, which add some effect to some other player over time
checked, if the targeted player had the upgrade himself.

It's of no interest, if the player who got hit by some effect has the
effect himself.
Added central effect handling library

The effect hub's goal is to handle all visual effects that can be shared
across upgrades and try to solve conflicts between those upgrades, that
use the same effect.

Currently only freezing a player completely in place and changing his
render color is implemented.
Icestab: Use effect library for freezing
Added Ice Grenade upgrade

Freeze a player in place when damaged by your grenade.