PLT-3412 WebRTC Server side & System Console (#3706)

* WebRTC Server side

* WebRTC System Console

* Consistency on variable names

* Add turn and stun uri validation

einterfaces/webrtc.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2016 Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package einterfaces
+
+import (
+	"github.com/mattermost/platform/model"
+)
+
+type WebrtcInterface interface {
+	Token(sessionId string) (map[string]string, *model.AppError)
+	RevokeToken(sessionId string)
+}
+
+var theWebrtcInterface WebrtcInterface
+
+func RegisterWebrtcInterface(newInterface WebrtcInterface) {
+	theWebrtcInterface = newInterface
+}
+
+func GetWebrtcInterface() WebrtcInterface {
+	return theWebrtcInterface
+}