various: implemented multiple project support

This required various changes to various parts of the infrastructure (mostly
using paths to finding the "root project" of any given object throughout).
Now theoretically infinite projects can be opened and accounted for at any
given time.

app/widget/panel/panel.cpp

@@ -20,6 +20,8 @@
 
 #include "panel.h"
 
+#include <QCloseEvent>
+#include <QDebug>
 #include <QPainter>
 #include <QStyle>
 #include <QStyleOption>
@@ -29,9 +31,12 @@ OLIVE_NAMESPACE_ENTER
 
 PanelWidget::PanelWidget(QWidget *parent) :
   QDockWidget(parent),
-  border_visible_(false)
+  border_visible_(false),
+  signal_instead_of_close_(false)
 {
   setFocusPolicy(Qt::ClickFocus);
+
+  connect(this, &PanelWidget::visibilityChanged, this, &PanelWidget::PanelVisibilityChanged);
 }
 
 void PanelWidget::SetMovementLocked(bool locked)
@@ -104,6 +109,28 @@ void PanelWidget::UpdateTitle()
   }
 }
 
+void PanelWidget::PanelVisibilityChanged(bool e)
+{
+  if (e) {
+    setFocus();
+  }
+}
+
+void PanelWidget::SetSignalInsteadOfClose(bool e)
+{
+  signal_instead_of_close_ = e;
+}
+
+void PanelWidget::closeEvent(QCloseEvent *event)
+{
+  if (signal_instead_of_close_) {
+    event->ignore();
+    emit CloseRequested();
+  } else {
+    QDockWidget::closeEvent(event);
+  }
+}
+
 void PanelWidget::changeEvent(QEvent *e)
 {
   if (e->type() == QEvent::LanguageChange) {