Add a batch_request_template flag

A virtual attribute to use to customise some info request behaviours
when we are using one request as a template for creating multiple
requests.
A batch template request should return a standard email subject.
Handle the application of censor rules to a batch request template.
Create a placeholder salutation for a batch request template.
Isolate code for preparing to display the compose interface.

Reuse it for the batch request page.
Work in progress on batch new