Implemented Bluetooth Low Energy gatt service and characteristics discovery

Bluez v4.x does not have total support for LE devices, a new approach, using gatttool command was implemented.

Auto-tests and documentation will be in other commits.

Change-Id: Iee711cc111199e15956052eebb7593bd3a5e27c8
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>