Refactor metric configurations for HTTP requests

- Restructured config to include 'http' with url and data fields for each metric. Added metrics 3 and 4 with specific data outputs.

config.example.php

@@ -7,7 +7,24 @@ $config = [
 	],
 	'app_demo_metric2' => [ 
 		'help' => 'Help text for metric',
-		'httpurl' => 'http://example.com', // The url to get collected for the metric
+		'http' => [
+            'url' => 'http://example.com', // The url to get collected for the metric
+            'data' => 'responsebody' // The body is used as output
+        ],
 		'jsonelem' => '0.metric',
 	],
+    'app_demo_metric3' => [
+        'help' => 'Help text for metric',
+        'http' => [
+            'url' => 'http://example.com', // The url to get collected for the metric
+            'data' => 'hasresponse' // If an error occured during request this will return 0, otherwise 1
+        ],
+    ],
+    'app_demo_metric4' => [
+        'help' => 'Help text for metric',
+        'http' => [
+            'url' => 'http://example.com', // The url to get collected for the metric
+            'data' => 'responsetime' // This will return the transfer time
+        ],
+    ],
 ];