Calendar/Agenda widget improvements

[dasgarner]

The calendar (3.0) / agenda (3.1) widget does some things which could be improved:

• Current event template is not assessed player side, meaning its out of date by the cache period
• The same is true for triggers
• We don't have the option to only show the current event
• 3.1 upgrade swaps calendar widgets over to agenda widgets, but that doesn't work on Layout import

[dasgarner]

I do wonder if this leads us to having the handlebars runtime available to widgets on the player, so that we could pass the template down (perhaps compiled if we can manage that) and have the player create events at runtime. This would need some thought of course!

[dasgarner]

3.1 upgrade swaps calendar widgets over to agenda widgets, but that doesn't work on Layout import

The decision here is to keep the Agenda widget which already existed as module type calendar and have the new Calendar widget have module type calendar-advanced so that they can coexist happily and imports still work, etc.

The titles of the respective widgets can stay modified to Agenda / Calendar respectively as the new names to make sense.

[maurofmferrao]

The swap between Agenda and Calendar to Calendar and CalendarAdvanced, as well as the "only show the current event" option are both developed in v3.