Ajaxify node rendering in calendar colorbox

#5433 
Currently (3.10, 3.11 and 3.x) each os_events view render all nodes in the view, so the colorbox will have them without extra requests. This cause long loading time.
To avoid it, we AJAXify the node loading, while still using colorbox. The simple quick solution is to use colorbox_node, but in the end we can grab just the code we want.
Perliminary tests showed reduce of 3 seconds in loading (of localhost/openscholar/www/economics/calendar)

WIP
First version using colorbox_node to ajaxify node rendering in calendar.