Adding a product to the basket with new parameter 'Quantity'

*Title: Adding a product to the basket with new parameter 'Quantity'.

*Documentation:
The new paramter 'Quantity' can be used when adding a product to a basket. 
In earlier versions of Exponential the shop did only add one product at a time.
With this feature you can add as many products of the same kind at once to the basket.

Example(node view template):

<form method="post" action={"content/action"|ezurl}>
	<label for="Quantity">Quantity</label><input type="input" id="Quantity" name="Quantity" value="" />
    <input type="submit" class="defaultbutton" name="ActionAddToBasket" value="Add to basket" />
    <input type="hidden" name="ContentNodeID" value="{$node.node_id}" />
	<input type="hidden" name="ContentObjectID" value="{$node.object.id}" />
    <input type="hidden" name="ViewMode" value="full" />
</form>