res_stasis: Extend bridge type to be a comma separated list of bridge attributes.

This change turns the bridge type field into a comma separated list of attributes.
These attributes include: mixing, holding, dtmf_events, and proxy_media. By setting
the various attributes a user can control the type of bridge created with the
behavior they need for their application.

(closes issue ASTERISK-23437)
Reported by: Matt Jordan

Review: https://reviewboard.asterisk.org/r/3359/
........

Merged revisions 410904 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@410905 65c4cc65-6c06-0410-ace0-fbb531ad65f3

rest-api/api-docs/bridges.json

@@ -26,18 +26,11 @@
 					"parameters": [
 						{
 							"name": "type",
-							"description": "Type of bridge to create.",
+							"description": "Comma separated list of bridge type attributes (mixing, holding, dtmf_events, proxy_media).",
 							"paramType": "query",
 							"required": false,
 							"allowMultiple": false,
-							"dataType": "string",
-							"allowableValues": {
-								"valueType": "LIST",
-								"values": [
-									"mixing",
-									"holding"
-								]
-							}
+							"dataType": "string"
 						},
 						{
 							"name": "bridgeId",
@@ -72,18 +65,11 @@
 					"parameters": [
 						{
 							"name": "type",
-							"description": "Set the type of bridge.",
+							"description": "Comma separated list of bridge type attributes (mixing, holding, dtmf_events, proxy_media) to set.",
 							"paramType": "query",
 							"required": false,
 							"allowMultiple": false,
-							"dataType": "string",
-							"allowableValues": {
-								"valueType": "LIST",
-								"values": [
-									"mixing",
-									"holding"
-								]
-							}
+							"dataType": "string"
 						},
 						{
 							"name": "bridgeId",