Down the water, tweak the u-boots, exclude nodes
- Dungeon masters cannot destroy nodes in excluded table neither nodes of
  group unbreakable, neither nether's nodes.
- Tweak of a global variable in seawrecks (aka. choosen_ingot)
- Highlandpools create real lakes now, and not water flower over the
  floor.
Oooops
- Missing modification on dungeon masters, I was exluding node only if I
  had to includ them... Things are correct now.