Make personal roboport area dependent on charge

[mrvn]

TL;DR

The construction area of the personal roboport should decrease when it looses charge servicing a smaller and smaller area.

What?

The construction area of the personal roboport should be 0 when it is out of charge and linearly increase to it's full range when it gains charge.

Why?

I just noticed that the movement bonus of the exoskeleton depends on it's charge and I think that would be a nice feature for the roboport too. Besides a nice gimmick this would also cause the construction bots to build nearby entities first, doing quicker work and using less electricity per entity until the roboport can catch up and recharge.