CRM-16734 Add participant tokens to participant pdf action

this would look like this
https://github.com/mallezie/civicrm-core/commit/2e6200a5700c65f6326244bd25ce77171f9046b0

I created a pull request: https://github.com/civicrm/civicrm-core/pull/8260

This pull request is a continuation of PR #8258, which provides event tokens for PDF letters to participants (CRM-16599).

I took the PR as part of the 4.7.8 code review process: please see the comments on the PR itself. Basically, this looks great, but it's so wide-ranging that it scoops up a handful of bugs in the process.

There are new commits since Andrew's QA so it is time to test again!

Would this also mean the participant tokens can be used in the scheduled reminder emails?
(Or would it be very hard to expand this to the participant emails?)

PR #9038 works for us since it allows us to use participant and event tokens (including custom fields) in PDF letters. But I don't think this is how we want to solve the issue in core CiviCRM.

What we really should do, is use a token processor to process the tokens. There is already an implementation of AbstractTokenSubscriber for events in CiviCRM, which is already used when you send scheduled reminders. But it doesn't support custom fields yet, afaik.

So imo, we should do the following:

• Create a token subscriber for participants
• Add custom field support to both token subscribers (Event and Participant); maybe we can use some of the code of PR 9038.
• Make CRM_Event_Form_Task_PDF use a token processor.

Once this is done, we can hopefully fix CRM-16579 in a similar way.

now trackied in https://issues.civicrm.org/jira/browse/CRM-16734