Add similar GUI than include paths has. Currently there is only
possibly select directories directly from the GUI. But filename
can be added to the path by editing it.
Handling paths in line edit control is quite hard. List control is
much more pleasant to use for it. Convert Project file path
handling to similar list control usage than include paths earlier.
Editing include directories in edit control is not nice. Instead
add new tab and list control for the include directories. They
are now added, edited and removed like global include directories
in settings dialog.
