Add DB patch to add cache columns for event talk/comment/tracks.
Update talk count cache when a new talk is added.
Update comment count cache when a new event comment is added.
Add method to update cached track count (not used currently).
Added it so that the full complement of helper methods is present.
Add cache counts to event detail API output.
Update tests to check for new cache counts.
tidy up database patch and put patch history entry as the last thing so we know it worked if we get that
don't allow talks to be created via the API that have no date given; we were defaulting to the current date and time
Merge branch 'richsage-cache-counts'