[Device] Add X_DLNA_PS transport action support

- Add the X_DLNA_PS transport action support to allow the
playspeeds provided by the renderer once we have provided it a
URI (SetAVTransportURI()) in addition to the renderer default
playspeeds retrieved via the introspection.
MINIMUM_RATE, MAXIMUM_RATE and TRANSPORT_PLAY_SPEEDS properties
will be upddated.

when SetAVTransportURI() action is called, MINIMUM_RATE,
MAXIMUM_RATE and TRANSPORT_PLAY_SPEEDS properties will be reset
with the renderer default playspeeds.

- The renderer default playspeeds are stored in the dlr_device_t_
structure to be re-used without having to be re-computed.

- When the application set the property RATE, the new rate value
is checked with either the renderer default allowed playspeeds or
the X_DLNA_PS allowed playspeeds depending on the availability of
the X_DLNA_PS.

- We now emit a property changed signal when application set the
DLR_INTERFACE_PROP_MINIMUM_RATE property with a value not equal
to the current one.

- For the parsing of the action string containing the X_DLNA_PS
content, thanks to regexp API, the sequence "\," are replaced
by "*" ("\," is used to separated the X_DLNA_PS speeds),
then the action string is splitted by "," to separate
each actions token. For getting the X_DLNA_PS playspeeds we then
just have to split the string with "*"

action string = Play,Stop,Seek,X_DLNA_PS=-8\,2\,4\,8

Signed-off-by: Christophe Guiraud <christophe.guiraud@intel.com>
[GUPnP] Output string parameter not initialized on success.

Fix https://github.com/01org/dleyna-renderer/issues/51

Check output string parameters before use, even if the command succeed.

Signed-off-by: Ludovic Ferrandis <ludovic.ferrandis@intel.com>