[FIX] mail: read ir.config_parameter with SUPERUSER_ID
[FIX] email_template: remove group restriction on field mail.compose.message.template_id

This was added as a security check, but access to this field is need by the wizard itself.
As non employee users can't read/create email templates, this will not be problematic
[MERGE] forward port of branch 7.0 up to 15ee4d8