Spammer Protection with ReCaptcha

I tested it reasonably well, i think. Just fill in the Public/Private key pair in ./upload/system/conf_main.php according to ./upload/install/include/conf_main_empty.php 

Let me know if you find bugs. I'll patch them asap. The whole problem with password hashing is more involved than expected, because Sharetronix have made it more complicated than necessary. Also, having no comments is a freaking sin in the authentication code...

Phil