Added more references to mod_proxy_* doc about websockets and load balancing.

<summary>

    <p>This module <em>requires</em> the service of <module

    >mod_proxy</module>. It provides load balancing support for

    <code>HTTP</code>, <code>FTP</code> and <code>AJP13</code> protocols

    </p>

    >mod_proxy</module> and it provides load balancing for

    all the supported protocols. The most important ones are:</p>

    <ul>

        <li>HTTP, using <module>mod_proxy_http</module></li>

        <li>FTP, using <module>mod_proxy_ftp</module></li>

        <li>AJP13, using <module>mod_proxy_ajp</module></li>

        <li>WebSocket, using <module>mod_proxy_wstunnel</module></li>

    </ul>

    <p>Load balancing scheduler algorithm is provided by not this

    module but other modules such as:

    <module>mod_lbmethod_byrequests</module>,

    <module>mod_lbmethod_bytraffic</module>,

    <module>mod_lbmethod_bybusyness</module> and

    <module>mod_lbmethod_heartbeat</module>.

    </p>

    <p>The Load balancing scheduler algorithm is not provided by this

    module but from other ones such as:</p>

    <ul>

        <li><module>mod_lbmethod_byrequests</module></li>

        <li><module>mod_lbmethod_bytraffic</module></li>

        <li><module>mod_lbmethod_bybusyness</module></li>

        <li><module>mod_lbmethod_heartbeat</module></li>

    </ul>

    <p>Thus, in order to get the ability of load balancing,

    <module>mod_proxy</module>, <module>mod_proxy_balancer</module>

    <p>This module <em>requires</em> the service of <module

    >mod_proxy</module>. It provides support for the tunnelling of web

    socket connections to a backend websockets server. The connection

    is automagically upgraded to a websocket connection:</p>

    is automatically upgraded to a websocket connection:</p>

    <example><title>HTTP Response</title>

        <highlight language="config">

Upgrade: WebSocket

Connection: Upgrade

        </highlight>

    </example>

    <example><title>Proxying requests to websockets server</title>

<p>Proxying requests to a websockets server like <code>echo.websocket.org</code> can be done using the

<directive type="ProxyPass" module="mod_proxy">ProxyPass</directive> directive:</p>

    <highlight language="config">

ProxyPass "/ws2/"  "ws://echo.websocket.org/"

ProxyPass "/wss2/" "wss://echo.websocket.org/"

    </highlight>

    </example>

<p>Load balancing for multiple backends can be achieved using <module>mod_proxy_balancer</module>.</p>

</summary>

<seealso><module>mod_proxy</module></seealso>