2.4.new mongo driver

Hi, a pull request for tags/v2.4.0 related to new mongodb driver api and new lift 2.6-RC1.
Related to https://groups.google.com/d/msg/rogue-users/A0ysQE2x3og/94rouuw_m1MJ
and 
https://groups.google.com/d/msg/liftweb/QSsjKLjhR9g/JMb9y4UPctYJ

this patch can apply to 2.4.0 and probably to v3

Thank you