Have NativeJavaPackage constructor that throws a ClassNotFoundException

When people misspell a class name with packages, e.g.

var ArrayList = java.util.ArrrayList
var a = new ArrayList()

they get an unhelpful error message:

TypeError: [JavaPackage java.util.ArrrayList] is not a function

We should add a @Constructor to NativeJavaPackage that simply throws a ClassNotFoundException to better inform the users of the nature of the error.