[FIX] ir_translation: validate translation values and do not sanitize them
[FIX] ir_translation: validate translation values and do not sanitize them

The value validation was de facto nullified by escaping invalid translations in
`XMLTranslator.process_text`.  Reimplement it by checking whether the
translated term can be translated back to its source term in the field value.
The sanitization of translated terms is now gone, as not all terms should be
sanitized (like attribute values).

bplancher/odoo,hip-odoo/odoo,Elico-Corp/odoo_OCB,laslabs/odoo,microcom/odoo,ygol/odoo,stephen144/odoo,bplancher/odoo,stephen144/odoo,laslabs/odoo,Elico-Corp/odoo_OCB,ygol/odoo,hip-odoo/odoo,storm-computers/odoo,microcom/odoo,storm-computers/odoo,Elico-Corp/odoo_OCB,stephen144/odoo,microcom/odoo,microcom/odoo,microcom/odoo,Elico-Corp/odoo_OCB,storm-computers/odoo,dfang/odoo,microcom/odoo,storm-computers/odoo,ygol/odoo,bplancher/odoo,Elico-Corp/odoo_OCB,hip-odoo/odoo,stephen144/odoo,hip-odoo/odoo,sysadminmatmoz/OCB,hip-odoo/odoo,sysadminmatmoz/OCB,sysadminmatmoz/OCB,ygol/odoo,dfang/odoo,laslabs/odoo,bplancher/odoo,dfang/odoo,sysadminmatmoz/OCB,sysadminmatmoz/OCB,sysadminmatmoz/OCB,storm-computers/odoo,storm-computers/odoo,stephen144/odoo,ygol/odoo,hip-odoo/odoo,sysadminmatmoz/OCB,laslabs/odoo,dfang/odoo,laslabs/odoo,dfang/odoo,bplancher/odoo,dfang/odoo,ygol/odoo,ygol/odoo,laslabs/odoo,stephen144/odoo,bplancher/odoo,Elico-Corp/odoo_OCB