[FIX] web: scroll handling for many2one selection

If the many2one selection height was too big (bigger than the browser page), it wasn't possible to see all options, because the body is set as overflow: hidden;

Moreover, if you opened a many2one selection and then scrolled the page, the selection moved with the scrolling, while it should be sticked to its input field

addons/web/static/src/css/base.css

@@ -3064,6 +3064,7 @@ div.ui-widget-overlay {
 }
 .ui-menu .ui-menu-item a {
   padding: 1px 16px;
+  color: #404040;
 }
 .ui-menu .ui-menu-item a.ui-corner-all {
   -moz-border-radius: 0;

addons/web/static/src/css/base.sass

@@ -2490,6 +2490,7 @@ div.ui-widget-overlay
         padding: 0
         a
             padding: 1px 16px
+            color: #404040
         a.ui-corner-all
             @include radius(0)
         a.ui-state-active

addons/web/static/src/js/view_form.js

@@ -3734,7 +3734,8 @@ instance.web.form.FieldMany2One = instance.web.form.AbstractField.extend(instanc
             // disabled to solve a bug, but may cause others
             //close: anyoneLoosesFocus,
             minLength: 0,
-            delay: 250
+            delay: 250,
+            appendTo: '.oe_view_manager_body'
         });
         // set position for list of suggestions box
         this.$input.autocomplete( "option", "position", { my : "left top", at: "left bottom" } );