feat: AudioSocket channel, application, and ARI support.

This commit adds support for
[AudioSocket](
https://wiki.asterisk.org/wiki/display/AST/AudioSocket),
a very simple bidirectional audio streaming protocol. There are both
channel and application interfaces.

A description of the protocol can be found on the above referenced
GitHub page.  A short talk about the reasons and implementation can be
found on [YouTube](https://www.youtube.com/watch?v=tjduXbZZEgI), from
CommCon 2019.

ARI support has also been added via the existing "externalMedia" ARI
functionality. The UUID is specified using the arbitrary "data" field.

ASTERISK-28484 #close

Change-Id: Ie866e6c4fa13178ec76f2a6971ad3590a3a588b5

rest-api/api-docs/channels.json

@@ -1810,7 +1810,8 @@
 							"allowableValues": {
 								"valueType": "LIST",
 								"values": [
-									"rtp"
+									"rtp",
+									"audiosocket"
 								]
 							}
 						},
@@ -1825,7 +1826,8 @@
 							"allowableValues": {
 								"valueType": "LIST",
 								"values": [
-									"udp"
+									"udp",
+									"tcp"
 								]
 							}
 						},
@@ -1866,6 +1868,14 @@
 									"both"
 								]
 							}
+						},
+						{
+							"name": "data",
+							"description": "An arbitrary data field",
+							"paramType": "query",
+							"required": false,
+							"allowMultiple": false,
+							"dataType": "string"
 						}
 					],
 					"errorResponses": [