Port RotThermal interaction logic from trunk premerge

Prior to the merge of two branches of ESyS-Particle to produce v2.0, the premerge trunk contained additional logic for thermal interactions between particles via conduction. This logic was temporarily dropped from ESyS-Particle for v2.0 and should be re-included. Since all the RotThermal logic was originally checked into SVN in a single check-in (rev. 926) the changelogs provide a roadmap for porting this logic across.