Support company logo in report
Ref https://discuss.tryton.org/t/company-logo-in-reports/25
We could reuse the same kind of design as for avatar and product image but using PNG (for transparency support).
The reports which display the company header must be updated to include conditionally the logo if it was set. The API must allow to request the logo to fit best a defined layout and return the image with the width and height and mimetype.