webadmin: Expose additional AuditLog fields to UI plugins

This change will allow additional fields in the
AuditLog(Event) object to be accessible by the plugin
API.  The new fields are as follows:
correlationId
message
callStack
customEventId
toString

Change-Id: I846b1e46e26dbff0d6b8c62eee0471555edc9bbf
Signed-off-by: Spenser Shumaker <sshumake@redhat.com>