tizen-volume-api: Implement client-side connection management

tizen-volume-api is a protocol extension that provides a better volume
management API for applications. This patch implements the interface
for connecting to module-tizen-volume-api and for tracking the
connection state.
tizen-volume-api: Add pa_ext_tizen_volume_api_bvolume

pa_cvolume doesn't allow storing balance information separately from
the overall volume level, so if the volume is set to zero, the balance
information is lost. "bvolume" tries to solve this by representing the
balance separately from the overall volume.
tizen-volume-api: Client API for volume controls
pactl: Add support for volume controls
New module: module-tizen-volume-api

The module implements the server-side code for handling the Tizen
volume API protocol extension. There is an implementation for all
volume control object operations, but there's no implementation for
the volume objects themselves, so this protocol extension is not yet
actually useful for applications.
tizen-volume-api: Add stub implementation of pa_tizen_volume_api

pa_tizen_volume_api is a singleton object that will keep track of all
volume control objects in the system (and any other objects that will
be needed in the Tizen volume API) and provide a hook interface for
getting change notifications.
tizen-volume-api: Connect to pa_tizen_volume_api from module-tizen-volume-api
tizen-volume-api: Introduce pa_volume_control
tizen-volume-api: Server-side implementation for the volume control client API
tizen-volume-api: Introduce main volume controls
tizen-volume-api: Client API for main volume controls
pactl: Add support for main volume controls
tizen-volume-api: Introduce pa_audio_group
tizen-volume-api: Client API for audio groups
pactl: Add support for audio groups
tizen-volume-api: Introduce pa_device
tizen-volume-api: Create device objects

pa_device_creator takes care of creating device objects for ports,
sinks and sources.
tizen-volume-api: Client API for devices
pactl: Add support for devices
tizen-volume-api: Introduce pas_stream