Merchants: era rules for merchant items (research requested)

[Dolalin]

Dagger of Symbols and Shadow Votex were completely new spells, so they should not be researchable until added. Those recipes should be blocked.

Summon Dead should NOT be blocked. It is a legit necro spell available from launch. It was only made available on vendors for the convenience of SKs when they got the upgrade from Haunting Corpse.

Still looking for research trivials but those don't seem incorrect at first glance.