Add class for new extension info table. Change Ranking() method to use mysql date expressions instead of silly unixtime math.
Add class for new extension info table. Change Ranking() method to use
mysql date expressions instead of silly unixtime math.

nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome