ui: Use window decorations on dialog windows (issue #376)

* added SubWindow flag to QtWindow to either use window decorations or show window within main window
* fixes black borders in some Linux window managers

bug id = 376

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src/lib_gui/qt/window/project_wizzard/QtProjectWizzard.cpp

@@ -51,7 +51,7 @@ QtProjectWizzard::QtProjectWizzard(QWidget* parent)
 
 QSize QtProjectWizzard::sizeHint() const
 {
-	return QSize(1000, 700);
+	return QSize(900, 600);
 }
 
 void QtProjectWizzard::newProject()
@@ -590,7 +590,7 @@ void QtProjectWizzard::newSourceGroup()
 	QtProjectWizzardWindow* window = createWindowWithContent(
 		[this](QtProjectWizzardWindow* window)
 		{
-			window->setPreferredSize(QSize(570, 420));
+			window->setPreferredSize(QSize(570, 380));
 			return new QtProjectWizzardContentSelect(window);
 		}
 	);
@@ -651,6 +651,7 @@ void QtProjectWizzard::emptySourceGroup()
 	QtProjectWizzardWindow* window = createWindowWithContent(
 		[this](QtProjectWizzardWindow* window)
 		{
+			window->setPreferredSize(QSize(470, 230));
 			return new QtProjectWizzardContentLanguageAndStandard(m_newSourceGroupSettings, window);
 		}
 	);

src/lib_gui/qt/window/project_wizzard/QtProjectWizzardWindow.cpp

@@ -9,7 +9,7 @@
 #include "qt/window/project_wizzard/QtProjectWizzardContent.h"
 
 QtProjectWizzardWindow::QtProjectWizzardWindow(QWidget *parent, bool showSeparator)
-	: QtWindow(parent)
+	: QtWindow(false, parent)
 	, m_content(nullptr)
 	, m_showSeparator(showSeparator)
 {