Add link button to Addon Manager to Macros dialog

Adds a button labeled Addons... to the macros dialog below the create, edit, delete, and rename buttons.  Clicking the Addons... button will open the same dialog available from Tools -> Addon Manager menu.
Convenience for experienced users, but new users who might not know about the addon manager will be able to see it here, too.

src/Gui/DlgMacroExecute.ui

@@ -277,6 +277,16 @@
          </property>
         </spacer>
        </item>
+       <item>
+        <widget class="QPushButton" name="addonsButton">
+         <property name="enabled">
+          <bool>true</bool>
+         </property>
+         <property name="text">
+          <string>Addons...</string>
+         </property>
+        </widget>
+       </item>
       </layout>
      </item>
     </layout>
@@ -298,7 +308,10 @@
   <tabstop>createButton</tabstop>
   <tabstop>deleteButton</tabstop>
   <tabstop>editButton</tabstop>
+  <tabstop>renameButton</tabstop>
+  <tabstop>addonsButton</tabstop>
   <tabstop>fileChooser</tabstop>
+
  </tabstops>
  <resources/>
  <connections>

src/Gui/DlgMacroExecuteImp.cpp

@@ -31,6 +31,7 @@
 #include "DlgMacroExecuteImp.h"
 #include "Application.h"
 #include "BitmapFactory.h"
+#include "Command.h"
 #include "MainWindow.h"
 #include "FileDialog.h"
 #include "Macro.h"
@@ -437,5 +438,15 @@ void DlgMacroExecuteImp::on_renameButton_clicked()
         }
     }
 }
+/**
+ * convenience link button to open tools -> addon manager
+ * from within macro dialog
+ */
+void DlgMacroExecuteImp::on_addonsButton_clicked()
+{
+    CommandManager& rMgr=Application::Instance->commandManager();
+    rMgr.runCommandByName("Std_AddonMgr");
+    this->fillUpList();
+}
 
 #include "moc_DlgMacroExecuteImp.cpp"

src/Gui/DlgMacroExecuteImp.h

@@ -51,6 +51,7 @@ public Q_SLOTS:
     void on_deleteButton_clicked();
     void on_editButton_clicked();
     void on_renameButton_clicked();
+    void on_addonsButton_clicked();
 
 protected Q_SLOTS:
     void on_userMacroListBox_currentItemChanged(QTreeWidgetItem*);