minor code refactoring

- face wrapper
- ndnrtc namespaces components
- new types PacketNumber, SegmentNumber and FrameNumber
- frame buffer updated to be used in key and delta namespaces
reverted refactoring

- removed introduced dedicated pipeliner class as it requires major
refactoring
- adjusted unit tests and frame buffer for using it in key and delta
namespaces
ref #1226 [Namespace update]

http://redmine.named-data.net/issues/1226
--
- added support for publishing in two namespaces: now video sender
publishes delta and key frames under separate prefixes - using
".../frames/delta" for delta frames and ".../frames/key" for key
frames.
before new refactoring
[in progress] refactored code

- re-designed fetching mechanism and frame buffer
ref #1226 - added InterestQueue class

- InterestQueue provides thread-safe prioritized interests expression
from one single queue. Prioritiy calculations may be customized by
subclassing from IPriority interface.
ref #1226. pipeliner startup algorithm debugging [in progress]

- added unit tests for debugging startup case for pipeliner
(pipeliner-test.cc)
- updated tests for video sender
ref #1226 - FrameBuffer fixes&features

- debugged new frame buffer (unit tests for Segment, Slot, FrameBuffer
classes)
- code cleanup
- small fixes, typos
ref #1226 chase estimation

- estimation of inter-arrival delay and it's growth used for making
decision about chasing state
ref #1226 Early working implementation of design v2
ref #1226 [renamed files]
ref #1226 [Design v2 early implementation]
ref #1226 [renamed "fetch-channel" -> "consumer"]
ref #1226 [Protocol v2]

- fixed major bugs
'issues/1226-key-frame-namespace' -> 'dev'