#374 Captchas

[Stefan Ilivanov]

To be added KeyCaptcha (https://www.keycaptcha.com/) and NuCaptcha (http://www.nucaptcha.com/) as additional captcha methods. Also captcha configuration to be moved in Administration/Settings. reCaptcha by Google currently have problems, it's avoidable by spammers bots, and empty registrations are not only in XOOPS with enabled reCaptcha.