Finishing combat update

Combat is good to go.
Can now use abilities and flee again.
Guarding reduces the HP damage of abilities by half as well now.
Made a lot of adjustments to abilities as part of this.
They now have to be told whether they can be used in combat and/or the
overworld (not implemented quite yet).
They also need to be given a defending equation (works opposite the
m_amount equation) in the PC's new UpdateAbilityDefendingAmounts
function.
m_amount = -PC->GetStats()->GetStr();
m_defendingAmount = p_defender->Getstats()->GetDef();
Changes HP equal to negative the player's strength plus the defender's
defense.