core: Add unregistering adapter powered callback
core: Add safe-guard to unregister ATTIO

This patch adds removes the source if the unregister ATTIO functions
gets called before the client is notified. This scenario can be
triggered if the client calls register and unregister in the same loop
iteration.
core: Trigger LE connections when powering on

This patch triggers the Bluetooth Low Energy connection when the adapter
is powered on and there is at least one client interested on ATT
connection.
core: Disable connection after local disconnection

This patch disables Bluetooth Low Energy re-connection after a local
initiated disconnection. ECONNABORTED is raised when the adapter is
powered off or when the user calls any disconnect method, for both
cases the re-connection will be triggered again when the adapter is
powered up or if the user calls device Connect method.
doc: Add Experimental GATT API
gatt: Add org.bluez.gatt.ServiceManager1 implementation
main: Register GATT ServiceManager1 on daemon init
test: Add an example for the gatt.ServiceManager1 API
.gitignore: Add test/gatt-service
bluetooth.conf: Add gatt.Service1 and gatt.Characteristic1
gatt-api: Minor clarifications about Descriptor property
gatt-service: Register one service and one characteristic object

Register both object with only skeleton implementations.
gatt-service: Add real values to the example service
gatt-service: Register the sample client with bluetoothd
gatt: Keep track of application implementing GATT services
gatt: Keep track of registered characteristics
unit: Add a test for child objects to test-gdbus-client
core: rename gatt.h to gatt_lib.h

Cosmetic change to avoid misleading between gatt library header and
the core generic attribute API header.
core: Avoid connection attempt if adapter is down

This patch avoids automatic ATT connection if the adapter is powered
off.
core: Removed unused parameter

This patch removes the unused "psm" parameter in
device_register_primaries function.