Port over the examples from arduino.cc/en/Tutorial/

[probonopd]

We should port over the example sketches for the Genuino 101 CurieBLE:

• https://www.arduino.cc/en/Tutorial/Genuino101CurieBLEHeartRateMonitor
• https://www.arduino.cc/en/Tutorial/Genuino101CurieBLEBatteryMonitor
• https://www.arduino.cc/en/Tutorial/Genuino101CurieBLEButtonLED
• https://www.arduino.cc/en/Tutorial/Genuino101CurieBLECallbackLED
• https://www.arduino.cc/en/Tutorial/Genuino101CurieBLELED

These have nice documentation and work with the Nordic smartphone app.

[sandeepmistry]

I think there are already too many examples in this library.

LED, LED callback, and LED switch (button) examples are already present.