watlaa + small fixes

• Watlaa connection, master mode (ie watlaa is master) - receives Libre packets and watlaa battery level

  This is a test version

  To setup Watlaa :

  • go to settings tab, select transmitter type Watlaa
  • go back to home screen
  • click transmitter
  • click start sensor and start the sensor
  • then go to the bluetooth tab (the second tab)
  • click the +
  • select watlaa
  • select watlaa master
  • scan
  • click 'done'

  xdrip should now receive the libre packets, you should get a calibration request

• Option to enable/disable nslog, see https://github.com/JohanDegraeve/xdripswift/wiki/NSLog

• fix #54, missed reading alerts goes on and on for ever

• fix #47, iPad crash when clicking transmitter button