* Factor test for auto save file into base frame class.
* Added auto save feature to Eeschema for saving schematics, addresses
launchpad question 173631.
* Add auto save interval control to Eeschema options dialog.
* Fix problem with subsequent auto saves in last commit.
* 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.
* Remove all occurrences if #ifdef USE_WX_ZOOM and all associated code within
the #else/#endif block ( old zoom code ).
* Removed the build option for USE_WX_ZOOM from CMakeList.txt and config.h.in.
* Removed all scaling code in base screen object.
* Fixed buffered paint and buffered client DC on Windows. Buffering works
properly on Linux and Windows.
* Modified kicad_device_context.h to automatically uses buffering on platforms
where double buffering is supported natively.
* Remove all of the scaled versions of the drawing functions in gr_basic.cpp
and any support code.
* Removed all traces of ActiveScreen global variable from eeschema and
gerbview.
* Renamed Recadre_Trace to RedrawScreen in draw frame object.
* Renamed PostDirtyRect to RefreshDrawingRect in draw panel object.
* Lots of code cleaning an Doxygen comment improvements.
* Use Boost pointer container for sheet hierarchy object.
* Add test for modification in sheet hierarchy list object.
* Add method to clear modification flag in sheet hierarchy list object.
* Improve Doxygen comments for sheet hierarchy list object.
* Remove redundant definitions in prototypes header file.
* Encapsulate file name member of base screen object.
* Encapsulate associated screen member of schematic sheet object.
* Create add screen method to schematic sheet object to simplify setting
the associated screen.
* Move the change file name code in the schematic sheet object to the edit
sheet method in the schematic editor frame object to eliminate message
dialogs.
* Improve reference counting in schematic screen object.
* Add helper type definitions for changing schematic object storage to C++
containers.
* Schematic reference object now completely encapsulated.
* Schematic reference list object refactoring complete.
* Make OK default button in PCBNew block operation dialog.
Eeschema: cleaning code. Start work to enhance annotation algorithm.
Already added an option to annotate using sheet number (sheet 1 uses numbers 100 to 199, sheet 2 uses 200 to 299..).
Works fine if deleting existing annotation, but needs work to be used when the existing annotation is kept .