Probe heat suggestion

[Ernos]

I have been playing another space sim, Take on Mars, and was thinking about the design choices we would have if we had to deal with the thermal limits of electronics. For example, probes need to have heaters installed or else they will drop below the magic -60C and not be functional until warmed up.

A way of implementing this would be to have all parts with a reasonable amount of electronics having a tag, like the probe cores or batteries, and a plugin watching for when they get below a certain temp, using the stock heating system. When they get below a certain point, the plugin renders them unusable until they are reheated. We could have like a base plutonium heater, and electrical heaters, and both be separate parts, and have them apply heat, like nuclear engines. The electric ones should be toggle-able, so you can disable them near the sun or during reentry or other heating events. It should be made in a way that we can choose not to have them if we are in atmosphere, like Kerbin, and they are heated enough by the environment.