gst/playback/: Add sink padtemplate to decodebin.

gst/playback/: Add sink padtemplate to decodebin.

Original commit message from CVS:
* gst/playback/gstdecodebin.c: (gst_decode_bin_class_init),
(gst_decode_bin_init), (find_compatibles), (close_pad_link),
(try_to_link_1), (no_more_pads), (close_link), (type_found):
* gst/playback/gstplaybasebin.c: (gen_preroll_element),
(remove_prerolls), (unknown_type), (add_element_stream),
(new_decoded_pad), (setup_source), (gst_play_base_bin_add_element),
(gst_play_base_bin_remove_element),
(gst_play_base_bin_link_stream):
* gst/playback/gstplaybin.c: (gen_video_element),
(gen_vis_element), (remove_sinks), (setup_sinks):
* gst/playback/gststreaminfo.c: (gst_stream_type_get_type),
(gst_stream_info_get_type), (gst_stream_info_class_init),
(gst_stream_info_init), (gst_stream_info_new),
(gst_stream_info_dispose), (stream_info_mute_pad),
(gst_stream_info_set_property), (gst_stream_info_get_property):
* gst/playback/gststreaminfo.h:
Add sink padtemplate to decodebin.
Added some more comments.
Make queue size configurable in playbasebin.
Added possibility to use elements as sinks (ex cdaudio).