sw-ajax.js: _sw_comet_last_activity_ts isn't used anymore; remove it.
REPLACE-PAGE: Reorder arguments to match with RELOAD-PAGE.
DEFAULT-REST-HANDLER: Add some more HTTP header junk to ensure there's no caching here.
Session: Handle :ONE-SHOT? "post-adjustment" correctly; this avoids temporary Session objects in the DB and also fixes an issue with -NUM-SESSIONS-MODEL-.