[REF] point_of_sale,web: move backbone to pos

This rev. moves the backbone library from web to pos, as one of its
two usecases (the search view) has just been removed. From now on,
it is only used in the pos.

Part of task 1893568

addons/point_of_sale/views/point_of_sale.xml

@@ -10,6 +10,7 @@
                 <link rel="stylesheet" type="text/less" href="/web/static/src/scss/fontawesome_overriden.scss"/>
             </t>
 
+            <script type="text/javascript" src="/point_of_sale/static/lib/backbone/backbone.js"></script>
             <script type="text/javascript" src="/point_of_sale/static/lib/waitfont.js"></script>
             <script type="text/javascript" src="/point_of_sale/static/src/js/main.js"></script>
             <script type="text/javascript" src="/point_of_sale/static/src/js/db.js"></script>

addons/web/views/webclient_templates.xml

@@ -185,7 +185,6 @@
         <script type="text/javascript" src="/base/static/src/js/res_config_settings.js"></script>
 
         <script type="text/javascript" src="/web/static/lib/jquery.scrollTo/jquery.scrollTo.js"></script>
-        <script type="text/javascript" src="/web/static/lib/backbone/backbone.js"></script>
         <script type="text/javascript" src="/web/static/lib/fuzzy-master/fuzzy.js"></script>
 
         <script type="text/javascript" charset="utf-8">