Sample Data Fixes - Memberships and Event Registrations

The current set of sample data in civicrm_generated.mysql contains Membership and Participant data which is invalid and confusing.

1. Many / most of the sample membership records contain End Dates which are earlier than the Start / Join dates AND invalid status values. For example:

Samuels, Anne Student July 4th, 2007 July 4th, 2007 July 4th, 2006 Check New

2. Contacts are registered twice for the same event. Listing for event 3 (Rain Forest...) returns these 4 rows:
Ms Jennifer O Łąchowski Sr
Ms Jennifer O Łąchowski Sr
Dr Michael O Smith Jr SmithMichael@hotmail.org
Dr Michael O Smith Jr SmithMichael@hotmail.org

... events 1 and 2 have similar issues (several duplicate participant records)

3. We should set civicrm_event.participant_listing_id = 1 for all 3 sample events in order to make it easier for folks to try out this new feature w/ the sample events.