Add Suspend/Resume support (#1535)

* Add Suspend/Resume support

* Support Suspend/Resume/Restart via API, UI and Systray

* Support screen lock/unlock scenario

* Handle idle scenario

* Align with fix for #1368

* Update Windows build

* Refactor SuspendHandler to maintain state

* Do not start BG-Effect, if system goes into suspend mode

* Correct Idle and Resume interaction

libsrc/api/JSONRPC_schema/schema-system.json

@@ -0,0 +1,20 @@
+{
+	"type":"object",
+	"required":true,
+	"properties":{
+		"command": {
+			"type" : "string",
+			"required" : true,
+			"enum" : ["system"]
+		},
+		"tan" : {
+			"type" : "integer"
+		},
+		"subcommand": {
+			"type" : "string",
+			"required" : true,
+			"enum": [ "restart", "resume", "suspend", "toggleSuspend", "idle", "toggleIdle" ]
+		}
+	},
+	"additionalProperties": false
+}