Proper exception handling in ResourceLoader. Catch exceptions and output them in...

Proper exception handling in ResourceLoader. Catch exceptions and output them in comments. Instead of just surrounding everything in a big try { } block, catch module-level exceptions where possible to allow error-free modules loaded in the same request to still be output normally. Modules that don't get output because of an exception are marked as missing in the client-side loader so other modules depending on them won't get loaded either.