Implement schema changes as described in this wiki document:
Includes design and implementing data model for "revisioning" of Activity records. Each activity record can have one and only one "current/latest" revision. There needs to be an easy way to discover:
- are there any older revisions for this Activity record?
- if so, get a list of the revisions with their Created Date and Created By information (created info stored in civicrm_log)