GUI: Add menuitem to close open project file.

gui/main.ui

@@ -76,6 +76,7 @@
     <addaction name="mActionOpenXML"/>
     <addaction name="mActionNewProjectFile"/>
     <addaction name="mActionOpenProjectFile"/>
+    <addaction name="mActionCloseProjectFile"/>
     <addaction name="mActionSave"/>
     <addaction name="mActionQuit"/>
    </widget>
@@ -374,6 +375,14 @@
     <string>Log View</string>
    </property>
   </action>
+  <action name="mActionCloseProjectFile">
+   <property name="enabled">
+    <bool>false</bool>
+   </property>
+   <property name="text">
+    <string>C&amp;lose Project File</string>
+   </property>
+  </action>
  </widget>
  <customwidgets>
   <customwidget>

gui/mainwindow.cpp

@@ -89,6 +89,7 @@ MainWindow::MainWindow() :
 
     connect(mUI.mActionNewProjectFile, SIGNAL(triggered()), this, SLOT(NewProjectFile()));
     connect(mUI.mActionOpenProjectFile, SIGNAL(triggered()), this, SLOT(OpenProjectFile()));
+    connect(mUI.mActionCloseProjectFile, SIGNAL(triggered()), this, SLOT(CloseProjectFile()));
 
 #ifdef WIN32
     connect(mUI.mActionHelpContents, SIGNAL(triggered()), this, SLOT(OpenHelpContents()));
@@ -690,6 +691,7 @@ void MainWindow::OpenProjectFile()
 
     if (!filepath.isEmpty())
     {
+        mUI.mActionCloseProjectFile->setEnabled(true);
         mProject = new Project(filepath, this);
         mProject->Open();
         QStringList paths = mProject->GetProjectFile()->GetCheckPaths();
@@ -708,12 +710,20 @@ void MainWindow::NewProjectFile()
 
     if (!filepath.isEmpty())
     {
+        mUI.mActionCloseProjectFile->setEnabled(true);
         Project prj(filepath, this);
         prj.Create();
         prj.Edit();
     }
 }
 
+void MainWindow::CloseProjectFile()
+{
+    delete mProject;
+    mProject = NULL;
+    mUI.mActionCloseProjectFile->setEnabled(false);
+}
+
 void MainWindow::ShowLogView()
 {
     if (mLogView == NULL)

gui/mainwindow.h

@@ -146,6 +146,12 @@ public slots:
     */
     void OpenProjectFile();
 
+    /**
+    * @brief Slot to close open project file.
+    *
+    */
+    void CloseProjectFile();
+
     /**
     * @brief Slot for showing the log view.
     *