Also commit updated icnos from Fabrizio.

compile base_screen.cpp separately for {pcbnew,cvpcb} and eeschema, so we can diverge internal units at compile time, not runtime

portrait setting was being overwritten in dialog_page_settings.cpp, add updatePortrait(), improve comments

    sizes.  Tested with postscript output only.  Required minor file format changes
    to reflect the "portrait" setting.  common/dialogs/dialog_page_settings.cpp
    uses a checkbox but its name is "Landscape", which is inverted from portrait,
    but since it is the more common choice, I used that rather than portrait.
    The tooltip for that checkbox makes it clear.  No portrait mode is supported
    for "User" paper size.

* Remove unnecessary copy constructors from board and module library
  objects.
* Add doClone() method to board and library objects.
* Add comment to class definitions where the default copy constructor
  generated by the compiler was adequate.
* Replace copy method with clone method where applicable.
* Remove DuplicateStruct() function.
* Remove track object copy function.

* Remove unnecessary copy constructors from schematic and component
  library objects.
* Add comment to class definitions where the default copy constructor
  generated by the compiler was adequate.
* Add assignment operator to EDA_ITEM, SCH_ITEM, and all schematic
  objects where the default assignment operator generated by the
  compiler would not be adequate.

This feature is very useful for electronics hobbyists who use DIY PCB technology 
(both toner transfer and photoresist methods).
Also width correction may be useful for PCB designers who take care of track width etching.
This patch also fixes some minor PS plotting issues.

* Move SCH_ITEM::Place() code into SCH_EDIT_FRAME so schematic item
  objects no longer have any knowledge of the schematic frame window
  or undo/redo containers.

Minor other enhancements and code cleaning.

* EDA_DRAW_PANEL completely encapsulated.
* Moved OSX m_overlay member from EDA_DRAW_PANEL to EDA_DRAW_FRAME where
  it is used.
* Doxygen comment warning fixes.

* EDA_DRAW_FRAME completely encapsulated.
* Encapsulate the the low hanging fruit in EDA_DRAW_PANEL.

* EDA_RECT and EDA_ITEM completely encapsulated.
* Removed unnecessary EDA_ITEM member m_Selected and replaced functionality
  with SELECTED flag bit.