Add bonus damage for knockback and combo ToonAttacks

[nosas]

The combo damage is straight-forward. The StackedAction class already handles actions targeting the same Cog.

The knockback damage is not as clear. More investigation is required.

Combo damage is just an extra 20% of all base damage dealt if multiple gags of the same type are used in the same round.

2 fogs do 100 total damage. 20% is 20, so in total, you deal 120 damage.

There used to be an old interaction of a level 7, ie wedding cake, getting combo on ALL cogs if even 1 other throw was used. This has since been changed, and only the cog hit with an extra gag gets the bonus.

Edit: Knockback is an extra 50% towards lured cogs with throw/squirt. This does not need 2 gags like combo. Both can be applied at the same time, but they do NOT buff each other. They both only boost from the base damage dealt.

Source: https://www.reddit.com/r/toontownrewritten/comments/184lx2y/bonus_damage_calculated/

[nosas]

Another source1 calculates the knockback bonus as a similar flat 50% of the summed base damage added onto the attack.

[nosas]

Done in #100, tests are required