Resolves the target class instance from the type name; accepts "source" or "build" or
a class name
@param type {String}
@returns {Maker}
function(type) {
      if (!type) {
        return null;
      }
      if (type.$$type == "Class") {
        return type;
      }
      if (type == "build") {
        return qx.tool.compiler.targets.BuildTarget;
      }
      if (type == "source") {
        return qx.tool.compiler.targets.SourceTarget;
      }
      if (type == "typescript") {
        throw new qx.tool.cli.Utils.UserError("Typescript targets are no longer supported - please use `typescript: true` in source target instead");
      }
      if (type) {
        var targetClass;
        if (type.indexOf(".") < 0) {
          targetClass = qx.Class.getByName("qx.tool.compiler.targets." + type);
        } else {
          targetClass = qx.Class.getByName(type);
        }
        return targetClass;
      }
      return null;
    }