Log views of contact, case and activity records for audit trail

Use Cases (from Physician Health)
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A supervisor wants to review what a staffer worked on.

Staffer wants to find something they filed yesterday, but can't remember enough details to locate via search. Reviewing the session log may help.

Organization wants to comply with HIPPA and be able to produce reports that include who VIEWED a medical record as well as edits.

Implementation
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1. Add 'operation' column to civicrm_log table. Enum, varchar or FK to option_values ??? Expected values are 'create', 'update', 'read' (and possibly 'delete')

NOTE: For existing writes to civicrm_log, if we can't easily distinguish add from update without lots of code modifications, we should think about another approach ('add/update' operation ??).

2. Insert a 'view' record in civicrm_log for the following user actions:

• contact view (contact summary tab) - civicrm/contact/view
• manage case - civicrm/contact/view/case
• activity view:
  • civicrm/case/activity/view
  • civicrm/contact/view/activity

3. We should probably allow sites to enable / disable this feature - can do so via constant in civicrm.settings.php for now.
CiVICRM_LOG_RECORD_VIEW
default = false

(If we figure out a way to enable this at the base DAO level, then we could potentially allow this constant to define an array of DAO's to log.)