calendar: reimpliment the pedalpalooza "month-long archive" view using the new codebase

[fool]

on the old site, http://www.shift2bikes.org/cal/viewpp2017.php looked like the below screenshot. I couldn't capture a long enough shot but at the bottom should be a day-by-day ride listing. @sdobz suggested that we could "remake" it using the new codebase since it's basically 3 things:

1. static: poster image for $year + header info which talks about dates and number of rides
2. dynamic: month-long calendar view
3. dynamic & existing already: long calendar listing by day

These are mostly linked from and used from the archive page (docs.shift2bikes.org/archive/pedal-palooza-archives/) and is more important than simply a record of what happened - it's also an inspiration to future ride creators to browse what happened last year and in the more distant past.

[fool]

I think @carrythebanner was working on this

[fool]

I could have sworn you showed off the archive pages like https://www.shift2bikes.org/archive/pedalpalooza/pedalpalooza-2018/ with event content, working on thursday @carrythebanner - am I misremembering? Now it seems to be just a header.

[carrythebanner]

This was implemented in #127 for PP pages (though still to-do is a generic all-year grid view).