Reworked and fixed selection of secondary skills:

- Fixed off-by-one error when checking for obligatory skills
- If both wisdom and magic school must be offered in the same slot, magic
school will be correctly offered on next levelup
- Obligatory skill can now be proposed for upgrade
- Obligatory skills are now offered using hero class weight instead of
simple random
- If hero has multiple skills not available to his class game will
select random skill instead of first one
- Moved storage of random seed to server instead of mutable member

lib/networkPacks/PacksForClient.h

@@ -1276,23 +1276,6 @@ struct DLL_LINKAGE ChangeObjectVisitors : public CPackForClient
 	}
 };
 
-struct DLL_LINKAGE PrepareHeroLevelUp : public CPackForClient
-{
-	ObjectInstanceID heroId;
-
-	/// Do not serialize, used by server only
-	std::vector<SecondarySkill> skills;
-
-	void applyGs(CGameState * gs);
-
-	void visitTyped(ICPackVisitor & visitor) override;
-
-	template <typename Handler> void serialize(Handler & h, const int version)
-	{
-		h & heroId;
-	}
-};
-
 struct DLL_LINKAGE HeroLevelUp : public Query
 {
 	PlayerColor player;