Added some metrics

	* variable\_rtp\_audio\_in\_skip\_packet\_count -
CHANNEL\_HANGUP\_COMPLETE - Histogram
	* variable\_rtp\_audio\_out\_skip\_packet\_count -
CHANNEL\_HANGUP\_COMPLETE - Histogram
	* Caller-Context.[context] - CHANNEL\_HANGUP\_COMPLETE - Counter
	* Caller-Source.[source] - CHANNEL\_HANGUP\_COMPLETE - Counter
	* Call-Direction.[inbound|outbound] - CHANNEL\_CREATE - Counter