Turn MjApi into EnergyApi to allow it to be re-used for other types of energy.

Would like to send some of my own energy,
through some of my own pipes, and use BuildCraft's energyApi to store it.

BuildCraft itself might even add another type of energy.

This would save people trying to add their own energy pipes,
from re-inventing the wheel, and copying TileGenericPipe.