Add dark oak and pale oak sapling to replaceable blocks

[RabbitTV22]

This would make the dark oak and pale oak sapling work by default with my plugin TerraTrees. Currently the pale oak and dark oak sapling wont grow because they cant replace the saplings.

[DeathShadez]

I'd say Overworld 2.0 will likely get these changes as that currently has the main focus over Overworld 1.0.