[ADD] packaging: windows: bundle wkhtmltopdf and lessc
[ADD] tools: handling of bin_path key in find_in_path

The openerp-server.conf now generates the bin_path record, in order
to resolve calls to external binaries served in the thirdparty dir.

Adpated report.py to use find_in_path and not directly which.
[FIX] packaging: windows: installer images odooification