Necromancer bug fixes and description adjustments

Adjusts several talents for Necromancers:

• The bone_explosion graphic for Shattered Remains now becomes more transparent as radius increases. A radius 6 graphic with full alpha is incredibly obnoxious, especially when it happens whenever a minion dies.
• Shattered Remains now doesn't affect the minion that's dying. Reduces log spam and unintuitive behavior with Boneyard.
• Shattered Remains now properly respects cut immunity.
• The Shattered Remains temporary effect now bounds the actor's HP on falling off or merging, to prevent (temporary) unusual behavior of creatures being at negative/zero HP without dying.
• Assemble will now attempt to find a free grid if the space occupied by the first skeleton is taken, usually by the skeleton reviving due to the effect of Boneyard. If it can't find one, it will re-kill the skeleton.
• The End of All Hope now displays the modified Dire Plague soul rip chance in its tooltip.
• Boneyard description now matches its behavior: it always resurrects regardless of talent level.
• Boneyard now resurrects minions at full HP. Resurrecting them at 0 HP is largely pointless and they'll die again immediately. The getResurrect getter is used to provide an entry point for scaling this value, perhaps with talent level.
• Necrotic minions decay by 15% of their max life each turn if they don't have a summoner or their summoner is dead. This is primarily to reduce the annoyance of facing Necromancer rares.

This MR is save safe, although some behaviors may not appear on currently existing minions.