***Add Color constants to ostd::Color
***Add MouseEntered/MouseExited callbacks
***Fix mouse detection currently using local coordinates
***implement file theme loading
***Implemenmt MouseDragged callback
***Add scissoring to only draw inside the bounds of containers
***Implement Drag And Drop
***Implement a way to determine on what widget (in the hierarchy chain) and event must stop
Add theme caching
Implement mouse scroll callback
Implement margin for widgets
Implement const in stylesheet
Implement color constants in stylesheet


Implement following widgets:
	***Label
	Button
		Image/Icon
	Panel / Container
		Title Label
	Checkbox
	Radio Button
		Grouping
	Text Input
	Horizontal Slider
	Vertical Slider
	Image / Icon
	ScrollView
	ListBox
	ComboBox
	TreeView
	Save/Open File Dialogs (and folder dialogs)
	Tab Panel