Introduced the MasterController as part of working on loading catalogue information.

Need a central piece to manage the catalogue data per database to prevent loading
this multiple times. MasterController is now also used to enable reopening the
connection manager from a query window after the connection manager has been closed.

mainwindow.ui

@@ -77,8 +77,15 @@
     <addaction name="separator"/>
     <addaction name="actionCancel"/>
    </widget>
+   <widget class="QMenu" name="menuView">
+    <property name="title">
+     <string>Window</string>
+    </property>
+    <addaction name="actionShow_connection_manager"/>
+   </widget>
    <addaction name="menuTest"/>
    <addaction name="menuQuery"/>
+   <addaction name="menuView"/>
    <addaction name="menuHelp"/>
   </widget>
   <widget class="QToolBar" name="mainToolBar">
@@ -238,6 +245,11 @@
     <string>F7</string>
    </property>
   </action>
+  <action name="actionShow_connection_manager">
+   <property name="text">
+    <string>Show connection manager</string>
+   </property>
+  </action>
  </widget>
  <layoutdefault spacing="6" margin="11"/>
  <resources>