added title for client/client_messages

interface/web/client/lib/lang/de_client_message.lng

 <?php
+$wb["page_head_txt"] = 'Kundenbenachrichtigung versenden';
 $wb["btn_send_txt"] = 'Absenden';
 $wb["btn_cancel_txt"] = 'Abbrechen';
 $wb["sender_txt"] = 'Absender-E-Mail-Adresse';

interface/web/client/lib/lang/en_client_message.lng

 <?php
+$wb["page_head_txt"] = 'Send customer information';
 $wb["btn_send_txt"] = 'Send email';
 $wb["btn_cancel_txt"] = 'Cancel';
 $wb["sender_txt"] = 'Sender email address';

interface/web/client/templates/client_message.htm

-<h2><tmpl_var name="list_head_txt"></h2>
+<h2><tmpl_var name="page_head_txt"></h2>
 <p><tmpl_var name="form_desc_txt"></p>
 
 <div class="panel panel_client">