Describe the bug
When attaching an immersive engineering cable to a backpack with a battery upgrade it is able to insert power into the backpack, but not extract power from the backpack

To Reproduce
Steps to reproduce the behavior:

1. Get a backpack with a battery upgrade
2. Fill the battery by attaching it to a power source
3. Attach the backpack to a machine via connectors and wires
4. See error

Expected behavior
It would be expected to give off power the same way it is able to take it, either by putting it next to a power input, or by connecting it via a wire

Versions
Minecraft - 1.16.5
Forge - 36.2.20
Sophisticated backpacks - 1.16.5-3.15.1.503
Immersive Engineering - 1.16.5-5.0.7-143

As far as I can see this is because connector only expects to receive energy and then shares it with network, but it doesn't actively extract energy from whatever it is connected to and SBP battery doesn't actively push energy out. I will think about whether I want it to push the energy and perhaps will just add that.

I will implement outputting the power in the future, but this one will be more involved as it will require being able to setup which side should output / input (or I guess it could also be both in some cases).