adding optional shutdown if no space for any output is left

As discussed in the channel, here's a simple pr.

This works even when all output resources would allow overflow and shuts
the converter down once there is no space to store any output anymore.

Useful in some cases (like with Universal Storage), not useful in others
(e.g. nuclear reactor that continues running if batteries are fully
loaded), so I introduced a KSPField defaulting to disabled.