ui: use icons in directory list box UI

bin/app/data/gui/setting_window/listbox.css

@@ -46,17 +46,11 @@ QtListItemWidget #button:hover {
 }
 
 #roundedButton {
-	background: dimgray;
-	border-radius: 8px;
 	color: white;
-	font-size: 15px;
 	height: 16px;
 	margin-right: 3px;
 	width: 16px;
-}
+	border: none;
-
-#roundedButton:hover {
-	background: gray;
 }
 
 #dropInfo {

bin/app/data/projects/tutorial/src/code_tutorial_2.h

@@ -47,10 +47,10 @@ void deep_thought()
 //  where does it come from?
 //
 // 3 - EXPANDING TO SCOPES
-//  Do you see first line of this snippet? I mean the one that has just two dots 
+//  Do you see the first line of this snippet? I mean the one that has just two
-//  as line number and reads "deep_thought". Actually that's the name of the  
+//  dots as line number and reads "deep_thought". Actually that's the name of
-//  function's scope that encapsulates the snippet. By clicking that line you 
+//  the function's scope that encapsulates the snippet. By clicking that line
-//  can tell Coati to expand the view to show the entire scope. 
+//  you can tell Coati to expand the view to show the entire scope.
 //  Give it a try!
 //
 //------------------------------------------------------------------------------

src/app/qt/element/QtDirectoryListBox.cpp

@@ -104,13 +104,13 @@ QtDirectoryListBox::QtDirectoryListBox(QWidget *parent)
 	innerLayout->setContentsMargins(8, 4, 8, 3);
 	innerLayout->setSpacing(0);
 
-	m_addButton = new QPushButton("+", this);
+	m_addButton = new QPushButton(QIcon("data/gui/setting_window/plus.png"), "", this);
 	m_addButton->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
 	m_addButton->setAttribute(Qt::WA_LayoutUsesWidgetRect); // fixes layouting on Mac
 	m_addButton->setObjectName("roundedButton");
 	innerLayout->addWidget(m_addButton);
 
-	m_removeButton = new QPushButton("-", this);
+	m_removeButton = new QPushButton(QIcon("data/gui/setting_window/minus.png"), "", this);
 	m_removeButton->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
 	m_removeButton->setAttribute(Qt::WA_LayoutUsesWidgetRect); // fixes layouting on Mac
 	m_removeButton->setObjectName("roundedButton");