Fixing vertical size of the design rules dialog to meet our minimal screen size requirement (768 pixels height)

* Changed line clipping function in gr_basic.cpp when USE_WX_ZOOM is
  enabled.
* Set wxDC clipping region to client size when drawing outside of paint
  event handler.
* Updated kicad and eeschema CMake files as the common library now
  requires linking to the polygon library.

* Corrected over zealous clipping fix in last commit.
* Tweaked clip box rectangle size.
* Fixed cross hair cursor drawing bug.

(two scrolling parameters were different when calling SetScroolBars in drawframe.cpp and hierarch.cpp 

* Fixed clipping bug when USE_WX_ZOOM is enabled that causes rats nest
  to be drawn incorrectly.
* Fix ambiguous function error in trigo.cpp when building with MSVS.
* Add instructions for building wxWidgets with graphics context
  enabled (GDI+) using MinGW/MSYS to COMPILING.txt.
* Initial EESchema find dialog work.
* Set modified flag when using PCBNew global deletion dialog to prevent
  closing without warning user of changes.

* Implement code to allow wxDC to handle coordinate conversions between
  device and drawing units.
* Add build settings to enable wxGCDC for wxGraphicsContext testing.
* Remove wxAUI conditional build cruft as it is now required to build
  Kicad.
* Fix scroll increment size regression to prevent jumping around the
  zoom center position.
* Add find GDI+ cmake module for building on WXMSW when wxGraphicsContext
  is enabled.

Some fixes.

Added sample gerber files for test (gerbview has problem with 2 files)

Added sample gerber files for test (gerbview has problem with 2 files)

Added sample gerber files for test (gerbview has problem with 2 files)

* Remove unnecessary options from EESchema print dialog.
* Expose page setup dialog to fix page orientation problems on wxGTK.
* Added custom schematic print preview frame.
* Print dialog and preview frame remember size and position settings
  between sessions.
* Added monochrome and print sheet reference settings to project file.

removed global variables and a lot of redundancies