Update ISPConfig behind http proxy

When running ISPConfig behind a http proxy (no direct web access) you must configure both php and wget/curl to use the proxy, which can be done by creating (or appending to) `/usr/local/ispconfig/server/lib/config.inc.local.php`:

Code:

<?php

# configure http proxy
$PROXY_HOST = "your-http-proxy.internal.tld"; // Proxy server address
$PROXY_PORT = "3128";    // Proxy server port
$PROXY_USER = "";    // Username
$PROXY_PASS = "";   // Password

# set environment variables for wget and curl
putenv("http_proxy=http://$PROXY_HOST:$PROXY_PORT/");
putenv("https_proxy=http://$PROXY_HOST:$PROXY_PORT/");

$defaultContext = array(
  'http' => array(
   'proxy' => "tcp://$PROXY_HOST:$PROXY_PORT",
   'request_fulluri' => true,
  ),
);

if (strlen($PROXY_USER) > 0 && strlen($PROXY_PASS) > 0) {
  $PROXY_AUTH = "$PROXY_USER:$PROXY_PASS";
  putenv("http_proxy=http://$PROXY_AUTH@$PROXY_HOST:$PROXY_PORT/");
  putenv("https_proxy=http://$PROXY_AUTH@$PROXY_HOST:$PROXY_PORT/");

  $PROXY_AUTH = base64_encode($PROXY_AUTH);
  $defaultContext['http']['header'] = "Proxy-Authorization: Basic $PROXY_AUTH";
}

stream_context_set_default( $defaultContext );

$conf['log_priority'] = 0; // 0 = Debug, 1 = Warning, 2 = Error