Improve documentation.
Improve documentation.

The documentation hyas been improved for the following examples:
* BLE_BatteryLevel
* BLE_Beacon
* BLE_EddystoneObserver
* BLE_EddystoneService
* BLE_LED
* BLE_URIBeacon
* BLE_Button

roywant/EddystoneBeacon,roywant/EddystoneBeacon