Update Timewood Clock to better reflect its description

[Caedis]

According to its own description

The Timewood Clock speeds up the growth of nearby plants, but does not speed up any other blocks such as Furnaces, nor accelerate the reproductive rate of Mushrooms.

Also stopped it from loading chunks of blocks it checks

Is IGrowable too broad, or should I change it to BlockBush?

#BlameDucked

[mgomezch]

This will also nerf mob farms using cursed dirt under spawners :(