Bundle fixture loader

Very basic functionality to allow insertion of Bundle products. Assumes that the bundle uses a Fixed price_type and each Option uses Radio.

Sample yaml: 
`
eav:
  catalog_product:
    - entity_id: 100
      attribute_set_id: 4
      type_id: bundle
      sku: b1
      name: "test bundle 1"
      short_description: "test bundle 1"
      description: "test bundle 1"
      url_key: b1
      bundle_options:
        1:  # option ID
          - 1  #child product ID
          - 90  #child product ID
        2:
          - 3 # child product id
          - 4 # child product id
      website_ids:
        - us
      category_ids:
        - 2 # Default Category
      price: 50.00
      price_type: 1 # Fixed
      tax_class_id: 2 # Taxable Goods
      status: 1       # Enabled
      visibility: 4   # Visible in Catalog & Search
`

Note that the selections are specified by product_id, so to prepare a buyRequest in the test, the following code is required: 

`      $bundleOptions = array(1=>array(1,90),2=>array(3,4)); //normally passed via dataProvider 
       $oBundleType = Mage::getModel('catalog/product')->load(100)->getTypeInstance();
        /* @var $oBundleType Mage_Bundle_Model_Product_Type */
        $cSelections = $oBundleType->getSelectionsCollection(array_keys($bundleOptions));
        $bundleOptionBuyRequest = array();
        //the provider and fixtures use product_id to identify a selection, but the buyRequest needs the selection_id
        foreach($bundleOptions as $optionId => $selection){
            $bundleOptionBuyRequest[$optionId] = $cSelections->getItemByColumnValue('product_id',$selection)->getSelectionId();
        }
`