Memory leak fixes



See merge request !640

When there is possible negative life the player's healthbar will now account for it and add a visual marker at the "0" health point too

Lord of Skulls now has images for all possible bone giants
Assemble now makes eternal before heavy (so in order of size)

Assemble correctly respects Lord of Skulls' right of uniqueness and will not merge it with the rest of the rabble!

Added new hooks "PartyOrder:define" and "PartyOrder:execute"

Pressing x on the levelup dialog can toggle between the current display and a new one were every value of talents over 5 levels is shown at once (just try it's harder to explain than it really is ;) )

Surge of Undeath now also heals minions
Necrotic minions can only be healed by themselves, other necrotic minions or talents that are not powered by nature

When Putrescent Liquefaction absorbs a dying ghoul/ghast, every two of them you'll get one soul back

Lord of Skulls now grants effects more gradualy and at the high end can now even affect a bone giant