Miscellanous bugs/UI improvements

Hello again,

This is a potpourri of fixes for the various bugs and inconsistent UI behaviour I discovered while working on part upgrades. The changes are:

- FNFusionReactor no longer generates spurious Charged Particles (it was hampering the max power draw of thermal rocket nozzles).
- FNNozzleController updates its Isp as soon as activated (or loaded, if previously activated). MechJeb (and presumably, Kerbal Engineer and others) is well pleased with this.
- FNRadiator correctly updates convected power when rapidly exiting atmosphere, also the VAB info for radiators no longer lists performance points at temperatures above the maximum.

Cheers