Implemented the LAYER_NUM typedef (LAYER was already taken as a class name...) to represent a layer number.

(meaning was inverted)

- Renamed ReturnMaskLayer to GetLayerMask (since it's a plain getter)

pcbnew: fix some cosmetic issues mainly on Linux ( these issues could be very dependant on wxWidgets/Gtk versions)

Fix many issues in config functions, mainly a rounding issue when a double is stored in wxConfig file (was stored only using 4 digits in mantissa)
Remove dead or obsolete code.

Fix rounding issue when a double is stored in a wxConfig file (wxWidgets 2.9.4 store only 4 digits in mantissa).
A new inline function ConfigBaseWriteDouble( config, key,  double_value )  is used instead of config->Write(  key, double_value ) which store 12 digits

pcbnew: fix print format in THROW_IO_ERROR
        fix properties file export_vrml.cpp

Drc_On => g_Drc_On
Route_Layer_TOP => g_Route_Layer_TOP
Route_Layer_BOTTOM => g_Route_Layer_BOTTOM
Track_45_Only_Allowed => g_Track_45_Only_Allowed

Pcbnew: fix an issue when texts in footprints have a size = 60 mils (default size for texts). After saving and reading the .kicad_pcb file, the size was not correct.

Pcbnew: Fix a collision name between 2 methods: EDA_ITEM::GetFlags() and ZONE_CONTAINER::GetFlags(), which creates a very strange behavior when creating/edition zones.
ZONE_CONTAINER::GetFlags() is now named  ZONE_CONTAINER::GetLocalFlags().

* Complete encapsulation of the ZONE_CONTAINER class.
* Fixed a bug in the EDA_TEXT::Format() default effects behavior due to
  improper conversion to internal units and missing test for default
  thickness.
* Improved grammar of some Pcbnew context menu strings.
* Moved some more cleverly hidden BOARD object methods into class_board.cpp.
* Lots of coding policy and documentation fixes.

standard layer name support from BOARD::GetLayerName().  This function evolved
in a contorted direction over time, and was being asked to return one of 3
different kinds of layer names, even though it only took a boolean to control
that choice.  

Users are better served by forcing them to get to know the concise new 
English Standard layer names.  This is because these concise names show up
in the "pretty" footprint/module files as the standard representation of
both feature and copper layers.

Change the name of BOARD::GetDefaultLayerName() to GetStandardLayerName().
Drop boolean argument to both BOARD::GetStandardLayerName() and 
BOARD::GetLayerName().

* Complete encapsulation of the MODULE class.
* Complete encapsulation of the EDA_TEXT class.
* Encapsulate most of the ZONE_CONTAINER class.
* Add pcbcommon library as a dependency for reSWIGging the scripting
  support.  This should cover most dependency cases.

checkcoding.py refactor from Edwin van den Oetelaar, some extra refactorings by me, improvement suggestions from Carl Poirier

Pcbnew: fix Bug #1156193 . Fix compil issues when KICAD_SCRIPTING_WXPYTHON is not enabled and KICAD_SCRIPTING is enabled