fix error looking up the WIFI_SERVICE

[mathisdt]

trackworktime/app/src/main/java/org/zephyrsoft/trackworktime/location/WifiTrackerService.java:50:
Error: The WIFI_SERVICE must be looked up on the Application context or memory will leak on
devices < Android N. Try changing  to .getApplicationContext()  [WifiManagerLeak]
  wifiTracker = new WifiTracker((WifiManager) getSystemService(Context.WIFI_SERVICE), basics.getTimerManager(),
                                              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   Explanation for issues of type "WifiManagerLeak":
   On versions prior to Android N (24), initializing the WifiManager via
   Context#getSystemService can cause a memory leak if the context is not the
   application context. Change context.getSystemService(...) to
   context.getApplicationContext().getSystemService(...).

[mathisdt]

fixed in 91cba28