Lower default heartbeat interval

Use 45 seconds as the default heartbeat interval instead of 60.  Using
60 causes connections to drop when proxied through Nginx as the default
timeout there is also 60 seconds.

docs/configuration.md

@@ -84,7 +84,7 @@ heartbeat interval it will be considered stale and closed.  A lower
 value means less time between connections going stale and them being
 closed.
 
-Defaults to 60
+Defaults to 45
 
 
 ### master.connector_shutdown_timeout

packages/lib/config/definitions.js

@@ -78,7 +78,7 @@ MasterGroup.define({
 	title: "Heartbeat Interval",
 	description: "Interval heartbeats are sent out on WebSocket connections",
 	type: "number",
-	initial_value: 60,
+	initial_value: 45,
 });
 MasterGroup.define({
 	name: "connector_shutdown_timeout",