Fix for a bug with imgAreaSelect: Use graph_height & graph_width from URL if present

The imgAreaSelect function in application/views/template.php always uses the conf['graph_height'] parameter:
jQuery('div.graph').imgAreaSelect({ handles: false, autoHide: true, fadeSpeed: 500, onSelectEnd: redirect, minHeight: '<?php echo $this->config->conf['graph_height'] ?>' });

If you modify graph_height or graph_width in the URL with h,w,graph_height or graph_width the imgAreaSelect calculation is wrong. This fix will store the parameters from URL in $conf array