Changed the attribute modification scale to make it more game-long suitable.

The attribute changes were very high or low alone, and with both the appliance
of equipment and battle effects, any monster/character could become either
a killer or almost harmless, even at high levels.
Fixed a dumb mistake in one of Harlequin skills.
Fixed a big gap in battle stats initialization.

I noticed that while fixing the modifiers. In fact, I forgot to apply the same
rule at battle start than when restarting a battle leading to erroneous values
obtained after removing an effect in certain cases.

It is now fixed.