[FIX]stock_landed_costs: Fixed wrong costs on landed costs with many products
[FIX] website_sale: displayed price doesn't change for 'List View of Variants' customize template
[FIX] product: Even when the product template has more than 1 variant, the default_code is displayed.
Merge pull request #2550 from odoo-dev/8.0-fix-default_code-chm

[FIX] product: Even when the product template has more than 1 variant, the default_code is displayed.
Merge pull request #2543 from odoo-dev/8.0-fix-website_sale-list-variants-chm

[FIX] website_sale: displayed price doesn't change for 'List View of Variants' customize template
[FIX] website blog: open change cover wizard at second selection

Fixes #2470
[FIX] models: correct lazy loading of manual fields
Merge pull request #2501 from hmen89/8.0-fix-write-compute-cost

[FIX]stock_landed_costs: Fixed wrong costs on landed costs with many pro...
[FIX] Report: compatibility issues on Windows

This commit fixes two different issues specific to Windows:
* NamedTemporaryFile behavior, requiring a file to be closed before being
  accessed a second time
* Wkhtmltopdf crash when the document's dpi is inferor to 96
[FIX] report: windows: lower level of file opening/closing, which to find wkhtmltpdf

* Use of 'which' to find the wkhtmltopdf binary (allow the win32 service to find it)
* Use of mkstemp and manual close of the file descriptors