All: fix a very minor issue: when a window is closed mazimized, and later reopened, it was not maximized.

fix an issue created by commit 2954. Gerbview: display now an indicator of layers in use. minor code cleanup.

* Move undo item copy global variable into schematic editor frame object
  member variable.
* Add helper methods for accessing the undo item copy member variable.
* Fix undetected bug when changing a text type.
* Added an exchange command to the undo/redo base class for handling undoing
  a changed item type which cannot be undone by swapping out the variables.
* Revert change to common/hotkeys_basic.cpp that broke hot key behavior.
* Lots of coding policy changes while making the changes above.

* Gerbview, Pcbnew: add SetLocaleTo_Default() after reading double in config to fix issues with decimal separator (when the separator is not a point).
(WxWidgets 2.9.1 seems call setlocale( LC_NUMERIC, "" ) when wxConfig read doubles stored in config, but forget to back to current locale.)
Note: perhaps there are some dialogs that need this call to  SetLocaleTo_Default() ).
* Minor  code cleanup in pcbnew/netlist.cpp

* store selected language by name instead of wx language id (that changes between wxWidgets version)
* accept always comma and point as flotating point separator.

* VERTEX INSERT: when dragging middle of a edge a new vertex is added there;
* VERTEX DELETE: when dragging vertex onto its neighbour vertex  they're collapsed into one.

* will not add zero-length segments when creating polylines;
* polyline vertex to edit is now being chosen correctly.

* Fixed minor code formatting issues with submitted patch.
* Change field name to "spice_model" per discussion with Charles McDowell.

* Change all code references to pin sheet and sheet label to sheet pin to
  more closely match the sheet pin object for improved code readability.
* Change menu and tool bar text from pin sheet to sheet pin for improved
  user readability.
* Moved sheet pin place method to sheet pin object source file.
* Move last sheet pin stored state information into schematic frame object.
* Add Doxygen comments for the sheet pin editing methods.

Fix an error in sch_field.cpp I created in bzr 2923 version, that prevent compiling with wxWidgets 2.9.1 (was not detected by 2.8.12)

* Rename EDA_Rect class to EDA_RECT.
* Rename EDA_TextStruct class to EDA_TEXT.
* Remove duplicate Doxygen comments from sch_sheet_path.cpp.

* Remove specialized edit reference, value, and foot print field methods
  from SCH_FRAME object.
* Improve general field method to handle all field types as this was
  essentially the same code used in the three methods removed.
* Updated the the hot key and context menu handlers to use the new field
  edit method.
* Minor Doxygen comment warning fixes.

fix 2 minor bugs: GERBVIEW: Button "Erase all layers" not working, EESCHEMA: Plot to Clipboard: EDA_DRAW_FRAME::PrintPage() error

* Push schematic back annotation code down into the appropriate class.
* Minor improvements to back annotate file selection code and user prompt
  strings.
* Minor tool bar tool tip capitalization fixes.
* Change tool bar ID error from message dialog to a debug assert message.

* Add item clarification context menu to EESchema when multiple unresolved
  items are found at the current cross hair position.
* Add collector class SCH_COLLECTOR for supporting multiple item hit testing.
* Removed bit wise masked filtering from schematic item hit testing.
* Removed all old hit testing functions and methods scattered about the
  EESchema source code.
* Move terminal point test function into SCH_SCREEN object.
* Fixed bug in terminal point test when terminating a bus to a label.
* Define the < operator for sorting schematic items.
* Add area calculation method to EDA_Rect item.
* Add method for returning an item's bitmap for menu display purposes.
* Add method for returning an item's menu text for menu display purposes.
* Changed EDA_ITEMS container from boost::ptr_vector to std::vector.
* Factor coordinate string conversion code from EDA_DRAW_FRAME to function
  CoordinateToString().