added new function field 'seller_id' to get main supplier who has highet priority in Supplier Information also 'seller_qty'.
added new function 'price_get' in 'product.supplierinfo' model to get price from supplier pricelist.
improved and clean product cost structure report in product form.
bzr revid: hmo@tinyerp.com-20100723131730-hx8nw4tkotmfj4ov