Fixed fire_dragonsnake with the new methods of the engine

The fire_dragonsnake is now more readable, has good sprites declaration,
the immobilization is good. Still one improvement to do : when you attack
his head while it is immobilized, the balls don't follow, make the head
can be very far of the first ball... Very ugly.
Add new dir for sprites effects reusable for several entities
Fixed problem with dragonsnake head

Refactor of wiznake (this enemy will not be used finally in the lost
palazzo), dragonsnake is now with a set_pushed_when_hurt to false
New lost palazzo rooms for boss/mini-boss

The boss room is fully functional
The mini-boss room has been completely changed to use the enemy giga and
not the wiznake.

TODO : code poisongiga and red_dragon boss (the sprites are almost done)