Progressive recipes despite disabling block levels

The goal was to fix #42 and register recipes that work despite disabling some block levels.

For that reason I've added a preInit(Block previousTier) to BaseBlock and preInit(Item previousTier) to ItemUpgrade. I'm not happy with the changes in the items part, but it's enough to fix the bug.
I would consider moving registering recipes out of each Block/Item and into a single (or one for blocks, 2nd for items) static class. At least for the tiered things, that use the previous tier in their recipe.

During fixing this bug, the Wooden Generator recipe got rearranged and the Cobblegen Upgrade recipe was changed. The latter could perhaps be changed to manually check for existence of stone, wooden and iron miner (in that order perhaps?) using the first found in it's recipe, or if only the diamond miner is active, a completely different item.