Made a step in removing knowledge of DatabaseWindow from QueryTab as an effort to move

in the direction of a plugin system.

DatabaseWindow now passes a Context to QueryTab and other pages that give those pages an
API for passing information up the system without knowing anything about the sytem.

pglab/PluginContentWidget.cpp

@@ -0,0 +1,18 @@
+#include "PluginContentWidget.h"
+
+PluginContentWidget::PluginContentWidget(IPluginContentWidgetContext *context, QWidget* parent)
+	: QWidget(parent)
+	, m_context(context)
+{
+
+}
+
+std::vector<QAction*> PluginContentWidget::getToolbarActions()
+{
+	return std::vector<QAction*>();
+}
+
+bool PluginContentWidget::canClose()
+{
+	return true;
+}