By Andy Silvester The Tory party manifesto, undeliverable and shaky though it was on the numbers, did have something going for it. The gradual abolition of national insurance to be replaced with a single income tax; more housebuilding; cutting the time it takes to get spades in the ground on major infrastructure projects. If you take it at face value and (perhaps more challenging) believe this current iteration of the oldest political party in the world is capable of delivering it, there wasn’t necessarily much to quibble with on the economic front. It is Labour’s test today, and it is fair to…