[Styles] Don't mention to use [style=QtStyle] selectors in comment

It is not available in current Qt releases

QzSchemeHandler+AboutDialog: Fixed coding style
[ToolButton] Cleanup code + removed unused properties
[ToolButton] Manually handle showing menu

ToolButtons now don't have menu indicators.
This fixes issue with Back/Forward buttons in Navigation Toolbar
being more wide than other buttons.
[ToolButton] New function to set look of button as it was in toolbar

Currently, it only sets the correct icon size
[Themes] No longer needed to set menu-indicator to none for ToolButtons
[ReloadStopButton] It is now only one button

Instead of hiding and showing two buttons (reload and stop), use
only one ToolButton and change the object name accordingly.