added number conversion in HTML value retrieval

Changes:
- number input fields now return numbers
- range elements removed since they are untested

Additions:
- added min and step specifiers to input fields associated to
  item number properties
- added a color hint for invalidity of
  item number input fields in actor sheet

src/templates/actor/partials/items-overview.hbs

@@ -84,7 +84,7 @@
             <img src="{{item.img}}" title="{{item.name}}" width="24" height="24" />
         </div>
         {{!-- amount --}}
-        <input class="flex05 item-num-val item-change" type="number" value="{{item.data.data.quantity}}" data-dtype="Number"
+        <input class="flex05 item-num-val item-change" type="number" min="0" step="1" value="{{item.data.data.quantity}}" data-dtype="Number"
             data-property="data.quantity" title="{{localize 'DS4.Quantity'}}">
         {{!-- name --}}
         <input class="flex3 item-name item-change" type="text" value="{{item.name}}" data-dtype="String"