Correct inconsistent behaviors in how additional participant statuses are updated when primary participant status is updated

Rules for processing
1. Make sure that the code which handles these status transitions is centralized into a single function regardless of where in the UI we are coming from (e.g. Edit Participant, Batch Update Participant via Profile, Change Participant Status, Edit Contribution, Update Pending Contribution Status). This ensures consistent behavior and means we can modify rules easily.

2. For now we will only cascade Participant status changes from the primary participant to the related additional participants:

a. IF the additional participant's pre-process status is the same as the primary participant

AND

b. IF we are doing ONE of these status transitions

• Pending pay later => Registered
• Pending pay later => Cancelled
• On waitlist => Cancelled
• On waitlist => Pending from waitlist
• Pending from waitlist => Registered
• Pending from waitlist => Cancelled
• Awaitlng approval => Cancelled
• Awaiting approval => Pending from approval
• Pending from approval => Registered
• Pending from approval => Cancelled

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Background here:
http://forum.civicrm.org/index.php/topic,10770.0.html