End to bridge encryption implementation

So far this is passing my basic tests, but could use some testing from people
that are much more familiar with how this is supposed to work.

Refs #27

bridge/bridge.go

@@ -48,6 +48,8 @@ type Bridge struct {
 	puppetsLock         sync.Mutex
 
 	StateStore *database.SQLStateStore
+
+	crypto Crypto
 }
 
 func New(cfg *config.Config) (*Bridge, error) {
@@ -104,6 +106,8 @@ func New(cfg *config.Config) (*Bridge, error) {
 		StateStore: stateStore,
 	}
 
+	bridge.crypto = NewCryptoHelper(bridge)
+
 	if cfg.Appservice.Provisioning.Enabled() {
 		bridge.provisioning = newProvisioningAPI(bridge)
 	}
@@ -151,6 +155,13 @@ func (b *Bridge) Start() error {
 		return err
 	}
 
+	if b.crypto != nil {
+		if err := b.crypto.Init(); err != nil {
+			b.log.Fatalln("Error initializing end-to-bridge encryption:", err)
+			return err
+		}
+	}
+
 	b.log.Debugln("Starting application service HTTP server")
 	go b.as.Start()
 
@@ -159,6 +170,10 @@ func (b *Bridge) Start() error {
 
 	go b.updateBotProfile()
 
+	if b.crypto != nil {
+		go b.crypto.Start()
+	}
+
 	go b.startUsers()
 
 	// Finally tell the appservice we're ready
@@ -168,5 +183,21 @@ func (b *Bridge) Start() error {
 }
 
 func (b *Bridge) Stop() {
+	if b.crypto != nil {
+		b.crypto.Stop()
+	}
+
+	b.as.Stop()
+	b.eventProcessor.Stop()
+
+	for _, user := range b.usersByMXID {
+		if user.Session == nil {
+			continue
+		}
+
+		b.log.Debugln("Disconnecting", user.MXID)
+		user.Session.Close()
+	}
+
 	b.log.Infoln("Bridge stopped")
 }