Eeschema: fix bug that crashes libedit (after creating a new pin, repeat it (insert key), delete the new repeated pin and try to repeat)

All: use double instead of int to store zoom values.

Speed up DIALOG_LOAD_ERROR::ListSet(), used to display lists of errors ( up to 100 x faster) in DRC or loading lib errors

* Change the minimum required CMake version to 2.6.4 for all build platforms
  except Windows and OSX.
* Move all schematic plot code from plot.cpp into the appropriate schematic
  objects.
* Create SCH_SCREEN plot method to plot all objects in the schematic
  screen.
* Delete plot.cpp and remove it from the CMakeList file.

Pcbnew: fix a minor issue.
Version update.

* Fix debug build warning (lp:793373).
* Changed sheet edit restore and undo to use object copy and replace method.
* Add minimum width and height constraints when resizing sheets that have
  hierarchical pins.
* Fix drag sheet hot key bug.
* Change Doxygen configuration to extract private methods and members
  when creating documentation.
* Fix a bunch of Doxygen comment warnings.

dialog_about: add translator name.

Libedit: actual line thickness  taken in account by collector. Thick lines are now more easy to locate. Fix incorrect boundary box calculations for LIB_PIN items. Very minor other fixes.

Pcbnew: fix very minor issue.

* Remove most (not all) variables that were initialized but never used that
  cause GCC 4.6 to generate a warning.
* Fix bug in schematic library editor best zoom calculation.

Pcbnew: bug fix: in rare cases, solid copper areas are to large (minimum width not taken in account to calculate filled areas)

Eeschema: bug fix: after a "De Morgan" convert command, the component was left selected (.m_Flags not cleared)

* Create library collector class.
* Add clarification menu to library editor when multiple items are found
  at the current position.
* Add get clarification menu text to all objects derived from LIB_ITEM.
* Add get menu bitmap for all objects derived from LIB_ITEM.
* Improve LIB_PIN bounding box calculation.
* Rename LIB_ITEM::DoGenCopy to doClone to match behavior defined in base
  class EDA_ITEM.
* Minor class renaming for improved code consistency.
* Added less than operator to EDA_ITEM.

gr_basic.cpp: fix a bug I created in my last commit. Pcbnew: fix a very minor bug in hight light behavior

gr_basic: fix incorrect clipping of thick lines (due to changes in code, the thickness was not taken in account to calculate the clip box size)

* Change class WinEDA_MsgPanel name to EDA_MSG_PANEL per coding policy.
* Change some old set message panel code in PCBNew with updated message
  panel methods in EDA_DRAW_FRAME.
* Remove unused global function Affiche_1_Parametre.
* Minor Doxygen warning fixes.

CMake: add definition KICAD_TESTING_VERSION and KICAD_STABLE_VERSION.
One of these 2 options *must* be now defined (i.e. run cmake with option -DKICAD_STABLE_VERSION or -DKICAD_TESTING_VERSION
Stable and testing branches should be more easier to maintain.