Fix whitespace/indentation (no functional changes)
Resume wi-fi scan after Wi-fi is turned on [#477]
Synchronize access to WifiScanner members

start()/stop()/getAPCount() and onReceive() are executed in different threads
and race conditions occurs.
Merge pull request #489 from illarionov/fixWifi

Resume wi-fi scan after Wi-fi is turned on [#477] (@illarionov)