minor fine-tunes

- marked some code as deprecated
- created designated attribute for pipeliner buffer size (current
number of pending interests)
- added logs for investigation of "jumping jitter bug"
(http://redmine.named-data.net/issues/1112)
ref #1109 [Audio/video synchronization], in progress

http://redmine.named-data.net/issues/1109
--
introduced new class AudioVideoSynchronizer which will maintain
audio/video playback synchronization logic between NdnAudioReceiver and
NdnVideoReceiver instances.
'issues/1109-av-sync' -> 'dev'
audio/video synchronization

- implemented intuitive approach for audio/video synchronization
mechanism
'issues/1109-av-sync' -> 'dev'
ref #1145 [High CPU load]

http://redmine.named-data.net/issues/1145
--
- dedicated thread for responding to FreeSlot events in frame buffer
- additional lock event for playout thread
'issues/1145-high-cpu-load' -> 'dev'
ref #1107 [Upon start fetching or publishing rendering window goes black]

http://redmine.named-data.net/issues/1107
'issues/1107-black-render' -> 'dev'
[untracked bugs]

- fixed issue with synchronization video -> audio
- fixed wrong frame buffer event handling
'dev'->'master'