[FIX][web] Detect image MIME.
[FIX][web] Detect image MIME.

Odoo v8 lacks a MIME autodetect method, but backporting the most relevant parts from v9, we can make it detect the image type and serve the correct header, to allow some client-side manipulations to work fine.

Daniel-CA/odoo,ehirt/odoo,spadae22/odoo,Daniel-CA/odoo,spadae22/odoo,spadae22/odoo,spadae22/odoo,Daniel-CA/odoo,Daniel-CA/odoo,spadae22/odoo,Daniel-CA/odoo,spadae22/odoo,ehirt/odoo,ehirt/odoo,ehirt/odoo,spadae22/odoo,ehirt/odoo,ehirt/odoo,Daniel-CA/odoo,ehirt/odoo,Daniel-CA/odoo