This commit moves the BLE GATT Battery service
from /samples/bluetooth/gatt to /subsys/bluetooth/services and
adds a Kconfig entry to enable and configure the service;
when enabled, it will register itself automatically.
Signed-off-by: Emanuele Di Santo <emdi@nordicsemi.no>
Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>
Emanuele Di Santo