The file system engine hosts for schematics were using a helper method to
read JSON files that was performing both an exist and read call. Besides
causing two file system calls, this also has a potential race condition
where the file may not exist by the time the read call is made. To avoid
this, a try/catch is used with the read call to handle the not existing
case.
Updates for all angular.io links to the new angular.dev domain. Additionally, adjustment to new resources where the equivalent does not exist on the new site (e.g. Tour of Heroes tutorial)
