Matrix: Setup bot, add PIN verification

PIN is verified but not used currently. Works a little different than
the others, you input your matrix user ID and then the PIN is sent to
you. The bot doesn't support E2EE, so the bot being the first one to
message ensures the chat is unencrypted.

main.go

@@ -100,6 +100,7 @@ type appContext struct {
 	email            *Emailer
 	telegram         *TelegramDaemon
 	discord          *DiscordDaemon
+	matrix           *MatrixDaemon
 	info, debug, err logger.Logger
 	host             string
 	port             int
@@ -590,6 +591,16 @@ func start(asDaemon, firstCall bool) {
 				defer app.discord.Shutdown()
 			}
 		}
+		if matrixEnabled {
+			app.matrix, err = newMatrixDaemon(app)
+			if err != nil {
+				app.err.Printf("Failed to initialize Matrix daemon: %v", err)
+				matrixEnabled = false
+			} else {
+				go app.matrix.run()
+				defer app.matrix.Shutdown()
+			}
+		}
 	} else {
 		debugMode = false
 		address = "0.0.0.0:8056"