[IMP] mail: update documentation of params in thread.xml templates
[IMP] mail: update documentation of params in thread.xml templates

Some parameters in the templates were not documented, which is now
the case with this commit.

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo