[IMP] email_template: add a lambda function to allow a user to format a date from...

[IMP] email_template: add a lambda function to allow a user to format a date from a template mail into a specific timezone, and/or in a specific format.

Eg: ${format_tz(object.name, object.employee_id.address_id.tz,'%m/%d/%Y %H:%M')}