添加API调用接口，添加读取分类，添加SpkUtils实用函数

使用了SpkSidebarTree子类实现对TreeWidget的特殊要求：不能取消选择，不能拖拽选择。

API调用接口暂时写死。API会获取

配置文件已添加但暂不使用。

gui/spkui_general.cpp

@@ -115,7 +115,7 @@ namespace SpkUi
     // FIXME: Chameleon style kept adding unwanted blue focus indication border
     // to widgets that shouldn't have borders.
     // We need to eliminate this irritating problem.
-    if(qgetenv("SPARK_NO_QSTYLE_CHANGE") == "1")
+    if(qgetenv("SPARK_NO_QSTYLE_CHANGE").toInt())
       return;
     OldSystemStyle = QStyleFactory::create("chameleon"); // TreeWidget doesn't work well with Fusion
     auto styles = QStyleFactory::keys();