WIFI autoconnect implementation

[代尔欣 <daierxin gmail com>]

Hi all,
        I am trying implement an autoconnect behavior like:
        User move outside of AP radio range. NM disconnect the AP. --- This
should already work with original NM.
        User move into the AP radio range again. NM autoconnect the AP just
disconnect. -- It seems NM0.7.0 or NM0.7.2 can't do this yet. Not sure the
NM0.8.0.