Allow tracker selection on the main calendar page
Currently the Calendar can get very large with lots of issues and quickly becomes unwieldy.
We would like the ability to specify which trackers to display on the calendar. Much in the same way as on the
"changelog" page. This will allow us to reducde the clutter on the calendar.
Ideally this would be available on the "my page" calendar as well as the main one.
It would probably be best to have a horizontal version of the tracker selection box that is currently displayed on the