By Vitalli Hnidyi KUPIANSK, Ukraine (Reuters) – The head of Ukraine’s railway vowed to keep trains running and to repair the damage done to the network by Russian troops, highlighting how rail is the lifeblood of the country and how the system is vital to restoring towns devastated during the invasion. Oleksandr Kamyshin, chief executive of Ukrainian Railways, spoke as he travelled by train through the Kupiansk railway hub, once used by Russian troops to resupply their frontline before the area was liberated by Ukrainian forces. Kupiansk was one of an array of settlements Ukrainian troops reca…