If a site has event logging switched to 'all' then the page activity
report will be based on event.ctime for the created/updated views
better reflecting what has changed during the timeframe.

If a site has event log switched off then the page activity report
will be based on view.mtime (last modified time) for the time period

behatnotneeded

Change-Id: I420dcbbb8be99146e8677ff3260484d72debd2a0
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>