Add a toolbar to mainwindow as global toolbar.
Remove file buttons from toolbox.
Cleanup code
Cleanup code and rename update_undo_redo to update_tools
Remove handlebox widget and tweak the toolbox layout.
Remove border of tool button of toolbox
Use smal icon size (16x16) for toolbar buttons
Add menu item names
Fine-tune UI layout of defalut widgets on toolbox
Add "Show Menubar" and "Show Toolbar" menu items to View
Add a separator to View menu and cleanup code
Method etl::shared_object::unref_inactive
This method allows to restore initial state of shared_object - reference
count is zero, but object exists. 'unref_inactive' decrease a reference
counter but don't deletes the object when count becomes zero.
ValueNode_Average
Make sure dialogs have their parent window set.

Influences following dialogs - Warning, Setup, OneMoment, About, Open, Save.
Set parent for some other dialogs.