New template tags

A small addition to our template editor. There are four new tags available:

• [[mailshot_id]] - Our internal ID of the mailshot, useful for generating mailshot-unique URLs.
• [[campaign_id]] - The internal ID for the campaign the mailshot is stored in, useful for agregating stats across multiple related mailshots.
• [[mailshot_timestamp]] - The time (as a unix timestamp) this particular mailshot was sent - will be the same for all messages in a given mailshot.
• [[message_timestamp]] - The time (as a unix timestamp) that an individual message was sent. Note that this will not be unique as we send several hundred messages per second.

If you're using tags like these for generating URLs for analytics purposes, remember that we have built-in Google analytics support which will automatically populate appopriate URL parameters without you having to do anything.