Improve lazy loading of event data to help cut down on initial render times

[rgriffith]

The main calendar page currently pulls in the YYYY/MM landing pages for the current year, plus the recurring events, which is 12 plus the number of YYYY folders. Instead, perhaps load only 1 or 2 YYYY/MM landings based on the current month. Also, switching to JSON format instead of XML may help improve performance a bit.

Another consequence of this is once the number of pages rendered by Cascade Server reaches 10 (including the calling page), the rendering metrics no longer load due to hitting the metrics cache limit.