Pcbnew: Force visibility of items which have no option in dialogs to controle this visibility, when reading the .kicad_brd file.
these options are used in GAL mode, but the usercannot control this visibility. So if the board file does not have these visibility flags set, the GAL never show them.
Fix also a compil warning.

Remove a few coverity warnings. Fix some comments which were incorrect, due to the changes in code. Remove not compiled code (kept as comments), now outdated or useless
legacy plugin: better compatibility with old brd files (current track width and current vias size, stored in SETUP section, were not read from file and incorrectly set)

 - CACHED_CONTAINER::GetVertices: removed useless and unused function
   which does nothing but tainted the API
 - SHAPE_LINE_CHAIN::Collide( const BOX2I& aBox, int aClearance ):
   removed an outdated function with assert(false)
 - SHAPE::BBox(): fix a small typo in the doc string

Pcbnew: fix  Bug #1422093 (pcbnew crashes after editing a footprint cominng from the board  with the fp editor and saving it on a librray and trying to load it to the board)
Some other very minor fixes.

Now OpenGL can report its problems instead of shutting down the application.

  Committing this separately from the rest to ease making a patch for just this
  functionality in case that it might make it into the trunk.
  
  This can function standalone, though it is less useful without the rest.
  It requires that wxwidgets-3.0.0_macosx_magnify_event.patch be applied to wxWidgets
  It is completely optional; everything is guarded by the USE_OSX_MAGNIFY_EVENT macro.
  
  - Added OnMagnify event handler to EDA_DRAW_PANEL, EDA_3D_CANVAS and the helper for
    EDA_DRAW_PANEL_GAL, WX_VIEW_CONTROLS. This should cover canvases all current tools.
  - Guarded all with USE_OSX_MAGNIFY EVENT feature macro and added support in CMakeLists.txt

Moved background color settings from GAL to RENDER_SETTINGS. Added RENDER_SETTINGS::TranslateColor() to convert between EDA_COLOR_T and COLOR4D.

Screen size is saved in VECTOR2I instead of VECTOR2D.