[storage] add delete method

src/main/haxework/storage/IStorage.hx

@@ -7,5 +7,7 @@ interface IStorage {
 
     public function read<T>(key:String):Null<T>;
 
+    public function delete(key:String):Void;
+
     public function clear():Void;
 }

src/main/haxework/storage/NoStorage.hx

@@ -13,4 +13,6 @@ class NoStorage implements IStorage {
     }
 
     public function clear():Void {}
+
+    public function delete(key:String):Void {}
 }

src/main/haxework/storage/SharedObjectStorage.hx

@@ -30,6 +30,13 @@ class SharedObjectStorage implements IStorage {
         }
     }
 
+    public function delete(key:String):Void {
+        if (exists(key)) {
+            Reflect.deleteField(so.data, key);
+            so.flush();
+        }
+    }
+
     public function clear():Void {
         so.clear();
     }