react to config change

Summary:
applets that acces their config in C++ needs to implement
configChanged() in order to still work correctly in the scripting
console

Test Plan: correct icon when created from scripting console and config written from there

Reviewers: #plasma, broulik

Reviewed By: #plasma, broulik

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D4461

applets/icon/iconapplet.cpp

@@ -66,6 +66,11 @@ void IconApplet::init()
     populate();
 }
 
+void IconApplet::configChanged()
+{
+    populate();
+}
+
 void IconApplet::populate()
 {
     m_url = config().readEntry(QStringLiteral("url"), QUrl());

applets/icon/iconapplet.h

@@ -45,6 +45,7 @@ public:
     ~IconApplet() override;
 
     void init() override;
+    void configChanged() override;
 
     QUrl url() const;
     void setUrl(const QUrl &url);