Add event before and after the search form

Identifier: search_body_form_before.html
Prosilver Location:

<!-- EVENT search_body_form_before -->

<form method="get" action="{S_SEARCH_ACTION}" data-focus="keywords">

Subsilver Location:

	<!-- EVENT search_body_form_before -->

	<form method="get" action="{S_SEARCH_ACTION}">

Explanation: Extensions may be designed to add secondary search options, such as Google search in the search_body.html. There are no events in the searchbody, so this should be merged.

Example: http://www.rising-dead.com/forums/search.php