fix(@angular-devkit/core): allow use of ResolverHost

Author: clydin

packages/angular_devkit/core/src/virtual-fs/host/index.ts

@@ -16,6 +16,7 @@ export * from './record';
 export * from './safe';
 export * from './scoped';
 export * from './sync';
+export * from './resolver';
 
 import * as test from './test';