JOINDIN-272 - Event comments - timezone offset

Hi,

This is fixes JOINDIN-272 issue. I've created a new helper ( **Which really needs a new name, but unsure what to go for** ).

I've applied the fix to the **_event_tab_comments.php** template, and it seems to work - tested on America/Montreal. **Defaults to Europe/London** if no Timezone is given in the Event.

Thanks,
Alan