Fixed layer picker for exporting to pcbnew
Realigned pcb layer name with class BOARD

More layer classification cleanup

Better description for entities on right click menu and panel
Typo fixes and some comment reformats

Gerbview, layer manager: add option (popup menu) to always keep layers not visible but the active layer, even when the active layer is changed.
Pcbnew: fix swig warning for operator EDA_COLOR_T::++  (changed to function EDA_COLOR_T:: NextColor)

In particular the new mechanism for handling extended color palettes is in place,
included renaming the ini keys and saving the color name instead of its index; this means better forward compatibility with palette changes.

Since ini keys are changed, colors will be reset

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

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

added option to allow zooming around the crosshair instead of the center; can be enabled via options or by holding alt while using the mousewheel

Gerbview: Fix a minor but annoying issue in gerbview  config: colors setup is broken when running a testing version after an old gerbview version (due to a bug of this old version which breaks the color config)

* Improve MSG_PANEL_ITEM to handle message panel information.
* Create containers for passing message panel items between objects and
  the message panel.
* Rename EDA_ITEM::DisplayInfo to EDA_ITEM::GetMsgPanelInfo.
* Remove all direct manipulation of EDA_DRAW_FRAME from all objects derived
  from EDA_ITEM.

Pcbnew: board editor: allows pad edition by hotkey 'E' (was accessible only by mouse button right click)
All: minor code cleaning and very minor bug fixes.

* Fix offset errors when scale factor greater is than one.
* Changed behavior of fit in page when not drawing border and
  title block to fit board outline in page.
* Fix offset errors when mirroring (still not 100% correct on MSW with
  wxWidgets 2.9.4).
* Lots of the usual code cleaning and simplifying.

MacOSX: disabling BufferedBitmap of OSX in gerbview, not supported nor accelerable and bitmap becomes too large in case of retina display to be usable

All: remove macros  MAX, MIN, ABS from macros.h and replace these macros by std::max, std::min and std::abs (mainly found in old code).

switch all <math.h> includes to <cmath> includes on an attempt to dodge some abiguous references to atan2()

Other minor fixes.

Code cleaning, minor fixes and minor coding style fixes. wxWidgets 2.9.4 compatibility fix( deprecated function MakeModal )