bridging: Add creation timestamps

This small feature will help to checking the bridge's status to
figure out which bridge is in old/zombie or not. Also added
detail items for the 'bridge show *' cli to provide more detail
info. And added creation item to the ARI as well.

ASTERISK-28279

Change-Id: I460238c488eca4d216b9176576211cb03286e040

rest-api/api-docs/bridges.json

@@ -753,6 +753,11 @@
 					"type": "string",
 					"description": "The ID of the channel that is the source of video in this bridge, if one exists.",
 					"required": false
+				},
+				"creationtime": {
+					"required": true,
+					"type": "Date",
+					"description": "Timestamp when bridge was created"
 				}
 			}
 		}