call-utils: inline call_new_with_streams()

We no longer support fallbacking to StreamedMedia so there is no point keeping
this static function.

https://bugzilla.gnome.org/show_bug.cgi?id=725070
empathy_call_new_with_streams: remove initial_audio arg

We always pass TRUE.

https://bugzilla.gnome.org/show_bug.cgi?id=725070
call-handler: remove 'initial-audio' prop

It was always set to TRUE anyway.

https://bugzilla.gnome.org/show_bug.cgi?id=725070
call-utils: use TpAccountChannelRequest higher level API

https://bugzilla.gnome.org/show_bug.cgi?id=725070
empathy-chat: use tp_account_channel_request_new_text()

https://bugzilla.gnome.org/show_bug.cgi?id=725070
share-my-desktop: use tp_account_channel_request_set_target_contact()

https://bugzilla.gnome.org/show_bug.cgi?id=725070
request-util: use TpAccountChannelRequest higher level API

https://bugzilla.gnome.org/show_bug.cgi?id=725070
tp-chat: use TpAccountChannelRequest higher level API

https://bugzilla.gnome.org/show_bug.cgi?id=725070
ft-handler: use TpAccountChannelRequest higher level API

https://bugzilla.gnome.org/show_bug.cgi?id=725070