To address #339

Remove array control on metrics data and add an autoconversion of PHP Object in PHP array.

For json request, i use the variable instead of label in metrics.

The variable names are lower case, without accent, without space (more stable than a label in a site).

includes/class-sp-player.php

@@ -96,7 +96,7 @@ class SP_Player extends SP_Custom_Post {
 			$metric = sp_array_value( $metrics, $key, null );
 			if ( $metric == null )
 				continue;
-			$data[ $value ] = sp_array_value( $metrics, $key, ' ' );
+			$data[ $key ] = sp_array_value( $metrics, $key, ' ' );
 		endforeach;
 		return $data;
 	}