First draft of the RTP Pack API

 * Introduce RTP Packet and Payload API implementation for Pack and Unpack
 * Introduce general handling of PI data and data type structures
 * Introduce the mutex encapsulation
 * Introduce a buffer pool manager
 * Example pack implementation in Encoder wrapper
 * Code Review comments

Signed-off-by: Singh, Ripinder <ripinder.singh@dolby.com>