Adds connectionsChanged signal to iface

This is meant to be used by plugins (DBManager is the
first candidate) to notify the application that
the GUI elements that handle connections needs to
be updated (i.e. the data source manager dialog
and the browsers)

python/gui/qgisinterface.sip

@@ -1256,6 +1256,15 @@ Get timeout for timed messages: default of 5 seconds
  \note
  added in version 2.7
 %End
+
+    void connectionsChanged();
+%Docstring
+ Emitted when connections have changed, this signal is forwarded
+ to the GUI elements that needs to be updated (i.e. the source
+ select dialogs and the browser widgets)
+.. versionadded:: 3.0
+%End
+
 };
 
 /************************************************************************

src/app/qgisapp.cpp

@@ -934,6 +934,8 @@ QgisApp::QgisApp( QSplashScreen *splash, bool restorePlugins, bool skipVersionCh
   mInternalClipboard = new QgsClipboard; // create clipboard
   connect( mInternalClipboard, &QgsClipboard::changed, this, &QgisApp::clipboardChanged );
   mQgisInterface = new QgisAppInterface( this ); // create the interfce
+  // Forward signal
+  connect( mQgisInterface, &QgisInterface::connectionsChanged, this, &QgisApp::connectionsChanged );
 
 #ifdef Q_OS_MAC
   // action for Window menu (create before generating WindowTitleChange event))

src/gui/qgisinterface.h

@@ -796,6 +796,15 @@ class GUI_EXPORT QgisInterface : public QObject
      * added in version 2.7
      */
     void layerSavedAs( QgsMapLayer *l, const QString &path );
+
+    /**
+     * Emitted when connections have changed, this signal is forwarded
+     * to the GUI elements that needs to be updated (i.e. the source
+     * select dialogs and the browser widgets)
+     * \since QGIS 3.0
+     */
+    void connectionsChanged();
+
 };
 Q_NOWARN_DEPRECATED_POP