gdbus: Don't call property changed callback during client init

When the client uses ObjectManager to init properties, do not call
property changed callbacks. They should only be called once the proxy
added has been successfully signaled since the proxy itself provides
a full copy of available properties.
gdbus: Fix missing PropertiesChanged signal

If D-Bus ObjectManager is not supported, InterfacesAdded signal
checking needs to be ignored otherwise PropertiesChanged signal
will never be sent.
bluez5: Rename BlueZ Profile registration functions

This patch renames external profile registration functions replacing the
prefix from 'bluetooth_' to 'bt_' in order to follow the name convention
adopted for bluez5 functions.
bluez5: Add support for Connecting/Disconnecting per UUID

This adds supports for sending the ConnectProfile() and
DisconnectProfile() messages for the org.bluez.Device1 interface.
hfp_hf_bluez5: Add Profile RequestDisconnection

This patch implements RequestDisconnection method of the Profile1
interface. This method gets called when the profile gets disconnected.
The profile implementation needs to cleanup the resources related to
the informed device.
hfp_hf_bluez5: Add support for Enabling/Disabling the modem

Now that we have the support for sending the correct messages
to BlueZ, we are able to dynamically power up/down the HFP modem.

We add another property to the modem to be able to get the D-Bus
object path that represents the remote device.
gdbus: Add g_dbus_proxy_set_removed_watch
hfp_hf_bluez5: Use some tricks to optimize code
hfp_hf_bluez5: Remove unneeded modem hash lookup

Modem object is created when the Device Proxy is added, and it is
paired. Another path is when the Device "Paired" property changes
to True.
include: Add ofono_modem_find
modem: Implement ofono_modem_find
hfp_hf_bluez5: Use faster method of disable()
hfp_hf_bluez5: Remove use of hash table

The number of paired devices is quite small, so the use of the hash
table for lookup seems unnecessary.  The typical user will have no more
than 1-2 devices paired, maybe half a dozen in a less common case.
hfp_hf_bluez5: Ensure active SLC for SCO links

Whenever a SCO connection is attempted, ensure that the SLC link is
already active between us and the same remote peer.
doc: Add experimental handsfree-audio API
dundee: Remove btio from dundee compilation
dundee: Rename dundee BlueZ 4 support

The BlueZ 4 support file for dundee has now been renamed to
bluez4.c to make it easier to add a BlueZ 5 support file.
dundee: Start BlueZ 5 support

This patch adds the BlueZ 5 support file for dundee.
bluez5: Add DUN_GW_UUID
dundee: Initial GDBusClient for BlueZ 5

This patch adds the callbacks to track additions and removals of
BlueZ related interfaces and property changes in these interfaces.