#4476: Different colors for selected/unselected objects

Added different and somewhat common for all visual object delta for
color changing when you select item so that making relation is easier.
#4497: Fixed unable to create link when any link is selected.
#4469: Added lines recognition and visualising.
#4503: Added GraphViewContextMenu(not connected)
#4405: Remade ContextMenu classes hierarhy.

Also, simplified searching for action.
#4431, #4504: Deleting nodes/links on Graph + Memory.

NOTICE: links are not seen to be selected so it is selected although you
don't see it.
'#4506: Painting fix, #4503: Added converter class
Known bug (will be reported):
- when converting object which has links, program crashes.
#4507: Fixed
#4472: connect nodes was added in graphviewcontextmenu