add CaptchaServlet

[ghost]

Please add CaptchaServlet.java(http://akiraly.github.com/cage/e02_servlet.html) class to a core of your lib.

[ghost]

With simperaptcha I can use

<servlet>
    <servlet-name>StickyCaptcha</servlet-name>
    <servlet-class>nl.captcha.servlet.StickyCaptchaServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>StickyCaptcha</servlet-name>
    <url-pattern>/stickyImg</url-pattern>
</servlet-mapping>

because StickyCaptchaServlet.java included in the core of lib.
So add CaptchaServlet.java class to a core of your lib.

[akiraly]

I have written one. I will add it shortly as a new module.